I had the same idea with the release of Dominaria. But I ended up with a UW control(ish) deck that also abuses Raff Capashen, Ship's Mage. He allows you to play your entire deck at instant speed.
Not really happy yet about the deck though. Manacurve is pretty high and the deck lacks some consistency.
Would like to fit in some countermagic to protect Raff (Rewind comes to mind, so you can untap and flash something in afterwards) and perhaps some Impulses.
I still felt like High Tide + Invocation works well for me, especially because I still run into 3-land issues quite often, which this combo works rather well. But further testing would be needed.
Why don't you just run more land? -3 High Tide, +3 Island seems like an obvious solution.
Also I don't see why you would want to splash white just for the Sunscorch Regents? If it's about the lifegain, green also has options for that. And Forgotten Ancient does equally well on the +1/+1 counters. I would get rid of white and simplify your manabase.
4 Raff Capashen, Ship's Mage
4 Jhoira's Familiar
2 Baral, Chief of Compliance
1 Mangara of Corondor
1 Danitha Capashen, Paragon
1 Shalai, Voice of Plenty
1 Lyra Dawnbringer
1 Radiant, Archangel
1 Akroma, Angel of Wrath
1 Zetalpa, Primal Dawn
1 Mox Amber
1 Blackblade Reforged
Enchantment
1 In Bolas's Clutches
Spells
4 Urza's Ruinous Blast
4 Preordain
4 Swords to Plowshares
3 Comeuppance
1 Aetherize
1 Reins of Power
8 Plains
5 Island
4 Irrigated Farmland
4 Sea of Clouds
2 Azorius Chancery
Not really happy yet about the deck though. Manacurve is pretty high and the deck lacks some consistency.
Would like to fit in some countermagic to protect Raff (Rewind comes to mind, so you can untap and flash something in afterwards) and perhaps some Impulses.
Why don't you just run more land? -3 High Tide, +3 Island seems like an obvious solution.
The only creature you can consider is Sakura-Tribe Elder, it can block and ramp.
This one seems a bit out of place here? Or am I missing something in the art?
Nice catch on Rishkar's Expertise, seems like a great inclusion.
Or Master of Waves if you want to the devotion route.
Kuldotha Forgemaster is a good tutor, especially with Ichor Wellspring and things like Spine of Ish Sah and Ugin's Nexus.
Hedron Archive and Thran Dynamo are good mana rocks for your Colossus.
Trading Post, Staff of Nin, Darksteel Forge and Predator, Flagship are other 1-ofs that I run for utility.
And since the Colossus doesn't have trample, Rogue's Passage can sneak your 10 damage through.
Buried Ruin would be a good replacement if Academy Ruins is out of budget.
Cut everything that is not an enchantment or Argothian Enchantress/Verduran Enchantress. The list MaelstromPonderer quoted is a good place to start.
Most has been mentioned already, but I would like to add that Open the Vaults could be a budget Replenish
I would maybe consider Mwonvuli Beast Tracker. It can find some of your utility creatures and stack your deck for Lurking Predators/Possibility Storm.
Also I don't see why you would want to splash white just for the Sunscorch Regents? If it's about the lifegain, green also has options for that. And Forgotten Ancient does equally well on the +1/+1 counters. I would get rid of white and simplify your manabase.
You should play the Prophet of Kruphix yourself
Could you share your decklist? I also want to try a similar deck: Burgeoning/Mystic Remora/Landfall
I was also thinking of putting these 2 together (now that Burgeoning has become affordable), but with a Landfall theme. Perhaps add some Rampaging Baloths, Ulvenwald Hydra, Seer's Sundial, Retreat to Kazandu, Retreat to Coralhelm, Prophet of Kruphix, Yavimaya Elder. I'm not really sure what else would fit in such a deck. Maybe you have some suggestions?