I'm not agreeing with the OP here, but you all seem to be missing a lost of the main point here: Turning plain creatures into enchantments or making enchantment creature tokens is about the lamest excuse for enchantment block design possible. There need to be cards that actually care about enchantments. Enchantresses. Things like Enchanted Evening, Three Dreams, or Greater Auramancy. Things that come together to make a unifying theme.
There's absolutely no reason for these to be equipments. None at all. If you just want artifacts that work better with creatures of the right color, do it like this:
Jar of Null Emnity 4
Artifact
~ costs 3 less to cast if you control a white creature. ,T, Sacrifice ~: Exile target creature. Its controller gains life equal to that creature's power.
You also have plenty of flexibility here. Instead of just "free equips" or a lowered mana cost, you could have a beefed up effect or extra bonus for creatures of the right color.
You'd have to pay RR for Reckoner unless you have more than one of this guy out.
Which is exactly what he said. A second one of this guy only costs 1. Turn 3 Ragemonger means you can cast a Ragemonger and three Boros Reckoners on turn 4 for just 1RRR.
Loremaster--Way too good. Giant Growth is insane, and anything that makes Giant Growth insane is scary. Or Hunter's Insight looped. Or Psychigenic Growth.
Chakar--Possibly too good, he either needs to cost more or put fewer counters on.
Bloodfang--Two cards at random is just too much, drop it to one. At two, nobody will *ever* do that. Furthermore, this has an awkward overlap with the Tribute mechanic in BnG. "Let something bad happen or make this guy bigger." I don't know that I like heroic stealing that effect.
Avenger--Interesting. Maybe Nyxborn Avenger? Definitely not Underworld.
Soul--I don't know what to think. It's interesting (ish) design space, but I don't like creatures that aren't actually creatures. This is just a modal sorcery (draw one card now or two when my guy dies), and it really ought to be templated as such.
Many, many people have designed mechanics around "gold counters" that you gain in various ways and spend in even more various ways. This is just a very, very narrow version of that and it does not allow for many interesting things.
If you want the damage to just gain counters, you'd need "Damage dealt by this creature gives you a glory counter." Much like infect/wither/lifelink/deathtouch. It's not a trigger, just a property of the damage. I don't like that though, there's no reason for it not to trigger. Infect/wither have perfectly valid reasons not to be triggered, in that it simply wouldn't work and it needs to replace the actual damage. Lifelink and deathtouch aren't triggers because they don't want lifelink to stack, and deathtouch would kill creatures both from the damage and the trigger and it made no sense. This ability should be able to stack in multiples, and doesn't actually replace the damage in any way.
2 2/2s isn't a good answer, and is arguably better than the single 4/4. 3 1/1s would probably be okay, and I see no problem with the emblem giving trample.
Just because you're not designing with them in mind doesn't mean that you should ignore it. These are the kinds of constraints that WotC has to consider, and good card design shouldn't just ignore things without good reason.
Innocent Blood wouldn't be any better. I think the answer is just not having a + ability that straight-up kills creatures.
I actually saw it as more of a nod to Psychic Drain. In fact, that'd be a decent emblem theme--"Whenever a card is put into an opponent's graveyard from anywhere, that player loses 1 life and you gain 1 life."
Garruk's +1 strikes me as probably too good. Primal Hunter only got a 3/3, which was very powerful, and he required serious color commitments.
Jace's emblem is very useless against mill, commander damage and poison. In fact, it just kills him 3 more times when you lose to an empty deck and just postpones death until the next state check against poison or commander damage.
Liliana's +1 might be too good. One-sided Abyss effect is insane, especially as it only makes itself harder to deal with.
The reason Inner Compass doesn't have to cost more than Rampant Growth is that even though it provides extra utility, it has a massive restriction. You can always cast Rampant Grown on turn 2. You can't cast this unless you dropped a creature on turn one. You can cast a topdecked growth regardless of your board state, but this is useless after a wrath.
Way too much to comment on everything here, so just a few that stood out to me:
Flourish (the second one on your list...) is the best storm card ever printed. EVER. Manamorphose is ridiculously powerful and it nets you no extra mana.
Float away is blue. To the best of my knowledge, green has never returnad a creature to its owner's hand. Just because it happens to hate on something green can hate on doesn't make it green.
Take flight is very punny, but I think it's on the wrong colors. Furthermore, it can't be done in mono-green or mono-red, so it really shouldn't be a one-mana hybrid.
Natural Aptitude might be undercosted. Will easily draw 3-4 cards for 3 mana in the decks that play it.
Aerial collision is nigh-unplayable. It's far too conditional to ever see anything other than sideboard in limited, and will only ever actually come into the main if your opponent has 10+ flying creatures in the deck.
At the beginning of your upkeep, gain control of all creautres and put two +1/+1 counters on each creature you control.
That's what it actually says. And that's nuts. Elesh Norn is a terrifying creature. This is a cumulative Norn every upkeep, but instead of only killing small creatures you steal them.
Yolov's second +1 should probabably be a -2. And its loyalty should probably be 4. The -8 is pretty bad, especially since it's useless in a Kraj EDH deck. I'd change it to "Search your library for any number of ooze creature cards..." instead of just Kraj.
For everyone losing their **** about the blue one: It only "plays the top card of your deck every turn" as long as you guarantee there are no instants, sorceries, planeswalkers, or enchantments in your deck. And when you have 5 untap triggers on the same turn, they're all wasted if the first card revealed is any of those.
The white one seems considerably better in practice. Both (typically) require attacking every turn to get their effect. The blue one is a dice roll as to whether you get anything, and whatever you get is not vulnerable to enchantment removal. There are no enchantment sweepers in the block, but there almost certainly certainly will be one in the same standard. The white one doesn't care if the things you find die, because it will just bring them back again. Sphinx synergizes with things that tap/untap him. White guy synergizes with enchantments.
It absolutely is a concern. It precludes them being used in many places where they'd make plenty of sense. Boros and Izzet could both easily lay claim--weapons that can defend on their own, or crazy contraptions--except there's absolutely no reason either would be creating things with black germs inside. They would use elementals or constructs.
You and target creature's controller bid life. You start the bidding with a bid of 1. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid. If you win the bidding, gain control of that creature.
That's the correct way to do this.
Jar of Null Emnity 4
Artifact
~ costs 3 less to cast if you control a white creature.
,T, Sacrifice ~: Exile target creature. Its controller gains life equal to that creature's power.
You also have plenty of flexibility here. Instead of just "free equips" or a lowered mana cost, you could have a beefed up effect or extra bonus for creatures of the right color.
Which is exactly what he said. A second one of this guy only costs 1. Turn 3 Ragemonger means you can cast a Ragemonger and three Boros Reckoners on turn 4 for just 1RRR.
Chakar--Possibly too good, he either needs to cost more or put fewer counters on.
Bloodfang--Two cards at random is just too much, drop it to one. At two, nobody will *ever* do that. Furthermore, this has an awkward overlap with the Tribute mechanic in BnG. "Let something bad happen or make this guy bigger." I don't know that I like heroic stealing that effect.
Avenger--Interesting. Maybe Nyxborn Avenger? Definitely not Underworld.
Soul--I don't know what to think. It's interesting (ish) design space, but I don't like creatures that aren't actually creatures. This is just a modal sorcery (draw one card now or two when my guy dies), and it really ought to be templated as such.
If you want the damage to just gain counters, you'd need "Damage dealt by this creature gives you a glory counter." Much like infect/wither/lifelink/deathtouch. It's not a trigger, just a property of the damage. I don't like that though, there's no reason for it not to trigger. Infect/wither have perfectly valid reasons not to be triggered, in that it simply wouldn't work and it needs to replace the actual damage. Lifelink and deathtouch aren't triggers because they don't want lifelink to stack, and deathtouch would kill creatures both from the damage and the trigger and it made no sense. This ability should be able to stack in multiples, and doesn't actually replace the damage in any way.
2 2/2s isn't a good answer, and is arguably better than the single 4/4. 3 1/1s would probably be okay, and I see no problem with the emblem giving trample.
Just because you're not designing with them in mind doesn't mean that you should ignore it. These are the kinds of constraints that WotC has to consider, and good card design shouldn't just ignore things without good reason.
Innocent Blood wouldn't be any better. I think the answer is just not having a + ability that straight-up kills creatures.
Garruk's +1 strikes me as probably too good. Primal Hunter only got a 3/3, which was very powerful, and he required serious color commitments.
Jace's emblem is very useless against mill, commander damage and poison. In fact, it just kills him 3 more times when you lose to an empty deck and just postpones death until the next state check against poison or commander damage.
Liliana's +1 might be too good. One-sided Abyss effect is insane, especially as it only makes itself harder to deal with.
Flourish (the second one on your list...) is the best storm card ever printed. EVER. Manamorphose is ridiculously powerful and it nets you no extra mana.
Float away is blue. To the best of my knowledge, green has never returnad a creature to its owner's hand. Just because it happens to hate on something green can hate on doesn't make it green.
Timberline guardian needs the Doran wording.
Take flight is very punny, but I think it's on the wrong colors. Furthermore, it can't be done in mono-green or mono-red, so it really shouldn't be a one-mana hybrid.
Natural Aptitude might be undercosted. Will easily draw 3-4 cards for 3 mana in the decks that play it.
Aerial collision is nigh-unplayable. It's far too conditional to ever see anything other than sideboard in limited, and will only ever actually come into the main if your opponent has 10+ flying creatures in the deck.
At the beginning of your upkeep, gain control of all creautres and put two +1/+1 counters on each creature you control.
That's what it actually says. And that's nuts. Elesh Norn is a terrifying creature. This is a cumulative Norn every upkeep, but instead of only killing small creatures you steal them.
Yolov's second +1 should probabably be a -2. And its loyalty should probably be 4. The -8 is pretty bad, especially since it's useless in a Kraj EDH deck. I'd change it to "Search your library for any number of ooze creature cards..." instead of just Kraj.
The white one seems considerably better in practice. Both (typically) require attacking every turn to get their effect. The blue one is a dice roll as to whether you get anything, and whatever you get is not vulnerable to enchantment removal. There are no enchantment sweepers in the block, but there almost certainly certainly will be one in the same standard. The white one doesn't care if the things you find die, because it will just bring them back again. Sphinx synergizes with things that tap/untap him. White guy synergizes with enchantments.
You and target creature's controller bid life. You start the bidding with a bid of 1. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid. If you win the bidding, gain control of that creature.