Requisition Raid - Staple. I was already considering Basri's Solidarity, but this is a huge upgrade. I believe is easily in the top 2 disenchant effects for white, with only Cathar Commando coming close.
Marauding Sphinx - IMO basically a blue Serra Angel, which is a decent baseline, even if you never get the crime trigger. Just 1 crime trigger makes it great.
Slickshot Lockpicker - A fun effect to have in peasant, and I love that plot offers the choice of delaying the payoff but getting a bigger spell.
Cunning Coyote - A great aggro card, and the plot here also allows for some fun decision-making.
Reckless Lackey - Checks the boxes for a strong 1 drop. Strong early and can be traded in when it's no longer useful. Also strong with auras/equipment/counters.
Aloe Alchemist - Another fun plot card. Already on curve even if you don't plot, but represents a lot of stats for 2 mana if the plot timing works out.
Spinewoods Armadillo - There's been a lot of 6 drops with land-cycling in green recently, and I think this is the strongest of them. Color fixing with some lifegain is nice on the cycle mode, and the creature mode is probably the strongest out of all of them.
Honest Rutstein - Card "draw" and ramp on a decently stated 3 drop is great.
Lavaspur Boots - This is the card I'm least sure about. It's like a colorless, equipment only version of Rabbit Battery. Haste for 1 mana equips is nice, but might not be enough.
Considering
Holy Cow - Lots of abilities that add up, but in a crowded slot.
Shepherd of the Clouds - I still play Serra Angel, and I considering swapping it out for this, but ultimately decided against it. Partially due to the 4 point of toughness, partially for the annoyance of the Shepherd having mount trinket text, partially due to nostalgia.
Stagecoach Security - One of the better anthems on a stick in white, and plot option is also an interesting choice here.
Geyser Drake - Seems like a good card and is some much needed support for the flash archetype, but blue 3 drops are pretty tight.
Desperate Bloodseeker - Decent stats but the mill needed to be slight better or repeatable.
Forsaken Miner - I'm not sure how easy committing crimes will be. I will end up including it if crime seems easier than I currently anticipate.
Hollow Marauder - I agree with ArBoR4817 above on 5 mana being decent and 4 being strong. But not sure what to cut to make room.
Demonic Ruckus - Competes against Madcap Skills and Sticky Fingers in my cube. 1 mana plot mode makes this interesting. Plot being face up makes getting blown out a little dangerous for my liking though.
Return the Favor - 2 interesting modes to have on 1 card, just feels like it might be too niche.
Rodeo Pyromancers - Feels like it should make double spelling pretty easy, but does nothing the turn it enters.
Cactusfolk Sureshot - Potentially strong, but I think I'd need to add more 4 power support in green/red to make it work.
Form a Posse - This starts to get good at MV 5-6. Not sure if that's good enough for a guild slot, or for go-wide decks to want.
On the Job - I'm interested in having at least a few mass pumps in white, and this seems like one of the better ones. +2 power at instant speed is where go-wide decks want to be, and the investigate is quite nice in case the game doesn't end.
Scuttling Sentinel - Flash, counters, protection and a reasonable base body, this guy does everything.
Maybe:
Fae Flight - Hexproof and then a slight buff and flying all on one card seems pretty good for 2 mana. Cartouche of Knowledge is completing for the same slot and I think I prefer the cantrip for now.
It Doesn't Add Up - Instant speed and menace seems like a pretty good combo, but 5 mana is a pretty steep cost for re-animation these days.
Leering Onlooker - A 1/3 flying for 2 isn't great, but creating 2 tokens in black from the graveyard is nice. I just wish the front end was a bit better.
Snarling Gorehound - An interesting effect. I think you need at least 3 surveils or a way to pump this guy to make the menace meaningful to be happy, and I'm not sure how often that will happen.
Convenient Target - Decent pump for aggressive decks and not-too expensive recursion. At first glance looks similar to Gryff's Boon. But I was looking at this against my 2 menace pump auras in red: Sticky Fingers and Madcap Skills and I'm not sure this is better than either.
Gearbane Orangutan - The 2nd mode is just a bit too situational in a regular cube to make this worth it imo.
Pick Your Poison - Going to rely on the creature versions for now, but the sacrifice should usually be fine for artifacts or enchantments, but the prevalence of flyers might make targeted removal more important for that mode.
Ordruun Mentor - Similar to Sunhome Stalwart, but the 3rd point of power is a big improvement for mentor. Being able to give other creatures first-strike is nice too.
Tribune of Rot - Pretty good in a best case where it can attack and get a decent trade (or even live) while milling some decent graveyard stuff and creating a 1/1. But it has to wait a turn and does nothing if it can't profitably attack.
Ecstatic Electromancer - A 3 MV 2/3 prowess is below rate these days, but the ETB and attack rummage can be pretty good.
Back in the day I played a good amount of Khan limited at my LGS. I never tried Valley Dasher in my cube because it only seemed average in its home limited environment as it eventually just killed itself. Being able to sac itself is nice upgrade, but spending 2 mana on that on like turn 4 after your opponent plays a 3/3 feels like a big tempo hit. I'll wait for reviews for before trying it.
Some cards in my cube that I was surprised by how few other cubes they were in:
Cenn's Tactician - (5 cubes) Seems like a good 1 drop that can stay relevant later in the game with just 1 spare mana, and boosts +1/+1 counters.
Law-Rune Enforcer - (16 cubes) This is just better than Gideon's Lawkeeper IMO. Colorless mana and 2 toughness are big upsides compared to the 2mv restriction.
Ninth Bridge Patrol - (3 cubes) Works with both aristocrats and flicker, I've seen it become must-kill size pretty fast.
Sunhome Stalwart - (28 cubes) Why isn't this a staple? Controls the board early, plays nice with +1/+1 counters and white go-wide/weenies.
Lulu, Loyal Hollyphant - (13 cubes) Discussed earlier in the thread, but I like this guy too. Requires some set up but can be pretty strong while supporting a lot of popular archetypes.
You're Confronted by Robbers - (14 cubes) 4mv for 3 bodies at instant speed is already decent, and the option to tap down blockers can force through an alpha strike if you already have the board presence.
Prison Term - (4 cubes) Maybe this is just a pet card, but I like that you can play this early and not worry about something stronger coming out later. Though it does have a weakness to sacrifice effects.
Fog Bank - (3 cubes) Seems like the perfect early road block for a control deck to slow down aggressive/midrange decks, and it has done well when I've seen it played.
Winter Eladrin - (32 cubes) Only pointing out that Man-o'-war is in more cubes despite being worse, I'm assuming for nostalgia reasons.
Aqueous Form - (2 cubes) Truthly I haven't seen this played in a while, but I remember how it used to do a lot of work for just 1 mana.
Foulmire Knight - (14 cubes) IMO the best 1mv deathtoucher and is never completely dead.
Death Denied - (6 cubes) Sure, it's inefficient when X is 1 or 2, but in the late game if X is at 3 or 4 it is just so much value at instant speed.
Dreams of Steel and Oil - (9 cubes) Has always been good early when I've seen it. Later on also has the potential to snipe a key card out of the opponent's graveyard too.
Moan of the Unhallowed - (9 cubes) At first I was surprised as I remember this card as being pretty popular a few years ago. But looking at this again I think this is probably just too slow now. I'll find a swap for this one.
Careless Celebrant - (7 cubes) Pretty easy for this to be a 2 for 1, or to kill a creature that cost a lot more mana. Makes combat hard for the opponent.
Livaan, Cultist of Tiamat - (5 cubes) Fun card for spellslinger that can make combat that interesting.
Top
Agonizing Remorse
Duress
Dreams of Steel and Oil
Decent
Drill Bit
Dread Fugue
Obsolete Or Not Great
Harsh Scrutiny
Blackmail
Cabal Therapy
Divest
I've never tried Inquisition. I imagine it's pretty good, but it used to cost too much, and now it doesn't interest me. I prefer the flexibility of Agonizing Remorse, Dreams of Steel and Oil, and the creature options.
Githzerai Monk is the only white high drop I've ever seriously considered being as scary as cloudgoat ranger, which is high praise. The effect on Malamet War Scribe takes a bad instant (inspired charge) and then overcharges you for a sorcery speed version of it. A 4/3 isn't even statted well at that mana cost. I'd much rather a card like Tenacity, rallying roar, rally to battle, make a stand, or even defend the campus. None of which I have ever considered running (although Tenacity does have a lot going for it on second glance)
I'd also throw in You Hear Something on Watch as an option, which feels like a more efficient version of Defend the Campus. I've never added it myself but I've come close to it.
Wild Things That Make My Heart Sing
4) Picklock Prankster- My blue section is becoming more and more graveyard based, so having a self-mill spell tied to a cheap defensive creature is awesome. A smidge underwhelming at 2UU, but you can pay in installments.
3) Cheeky House-Mouse- A 2/1 for W with some late-game relevance. White has a deep roster of good 1-mana creatures now.
2) Stormkeld Vanguard- A great combination of cheap Naturalize plus big chonker. Vanguard will crowd out a similar card, but I expect great results from this.
1) Embereth Veteran- A historic 2/1 for R at Peasant. The sacrifice is not the biggest upside, but that Young Hero Role could take an 2/1 flier all the way up to a 5/4 after a few attacks. Looking forward to more red 2/1s in the future.
Not a fan of Bitter Chill? That was the only instant include of mine I didn't see on your list.
With the addition of Generous Ent there's now a lot of pretty good land cyclers (some of which ramp) on beefy green creatures. How would you all ranks these?
Preening Champion - Very strong, but it's up against Aven Eternal. Aven Eternal has incidental +1/+1 counter synergies, this is better when blinked IMO, very close call.
Xerex Strobe-Knight - Potentially very strong if you get just 1 activation. Still decent even if you don't.
Seer of Stolen Sight - 3 mana 2/3 menace isn't great, and there's been creatures that scry off creatures dying before, but this is the first decent surveil one IIRC. Helps with aristocrat and graveyard synergies.
Fearless Skald - High power for a double-striker, or you get a combat trick.
Kami of Whispered Hopes - Ramp and +1/+1 counter payoff in 1, but requires help to get the counters going.
Tandem Takedown - Instant, one-sided, your creatures get pumped, and you get 2 creatures to do it. This gives a small pump in exchange for an additional G pip over Band Together
Halo Forger - High ceiling if there's a spell to cast right away, but potentially clunky if there isn't
Cut Short - Swift Response except 1 more mana but convoke. White is probably the color that can take advantage of convoke the most, but I don't think the extra mana is worth it.
Saiba Cryptomancer - Potentially nice combat trick, blink target, and holder of auras/equipment, but has a high chance of being bad if it's just a 1/2
Bladed Battle-Fan - Cool protection spell/equipment combo, but I wish the equipment did more
Gloomfang Mauler - Nice big beater with self-discard for reanimation or to hit early land drops. Backup effect is potentially interesting. The cycling + ETB help ensure a high floor, but a 7 mana 7/7 menace still is only a decent ceiling.
I'm surprised to not see discussion on Annihilating glare. Bone Shards and Eaten Alive are the closest competition. Annihilating Glare seems the most generically strong, but I guess Bone Shards' discard mode is useful for reanimator.
Considering
Maybe:
Agonizing Remorse
Duress
Dreams of Steel and Oil
Decent
Drill Bit
Dread Fugue
Obsolete Or Not Great
Harsh Scrutiny
Blackmail
Cabal Therapy
Divest
I've never tried Inquisition. I imagine it's pretty good, but it used to cost too much, and now it doesn't interest me. I prefer the flexibility of Agonizing Remorse, Dreams of Steel and Oil, and the creature options.
I'd also throw in You Hear Something on Watch as an option, which feels like a more efficient version of Defend the Campus. I've never added it myself but I've come close to it.
Not a fan of Bitter Chill? That was the only instant include of mine I didn't see on your list.
Considering
Interesting but Probably Not