Thanks, dude!
So. I figure I might as well detail a lot of the big top level changes from my initial sketch. Firstly, I finally caved and included fetches. I hadn't included them for a few reasons. 1) The extra shuffling is kind of a pain. 2) They have the potential to make mana too good, and I like it when people have to be disciplined with their splashes. 3) They're goddamn expensive and I only actually own about half of them. Modern Horizons finally tipped the scales for me with the lands in graveyard theme, and Wrenn and Six is just too cool not to include, but dude just doesn't work without fetches. The upshot is that fetches really do turn on a ton of cool stuff like Titania and Crucible of Worlds.
Second, I have the archetypes for each color pair locked in.
Azorius - Spirits and blink (and blinking spirits).
Dimir - Steals your stuff and beats you to death with it.
Rakdos - Aristocrats
Gruul - Literally throwing lands at your face.
Selesnya - A midrangey token control strategy, kind of like the old GW manifest decks.
Orzhov - Resilient aggro and reanimator (sometimes both). Ayli is a placeholder for the new BW zombie knight from M20
Golgari - All hail the hypnotoad. I mean, graveyard stuff.
Simic - basically the stuff Simic is doing in standard right now.
Izzet - Spells. It's a classic for a reason. I'm trying to slant it a little more aggressive than it's been in the past where it's been more of a control strategy.
Boros - This is an experiment. We're slotting in Feather and Tenth District Legionnaire and a few more combat tricks. There are also a bunch of modal spells where one of the modes targets one of your own creatures. I'm not sure this actually works in an environment with this power level, but I want to try. It's a shame most of the actual heroic creatures kind of suck.
Third, Planeswalkers. I settled on 10 monocolored walkers, a male and a female for each color. I don't feel great about leaving Elspeth, Sun's Champion out since it's one of my favorite cards of all time, but I can't not include Serra. I've been crushing on Serra since I was 10. I'm also a little concerns about Davriel's power level, but Ob Nixilis is soooooo boring and I really want to include both 3 mana Lili's but I've got a whole theme going and I'm too stubborn to change it. I also threw in a bunch of the WAR hybrid walkers. I'm taking a lot of design cues from WAR in general about how to design a limited format with access to a bunch of planeswalkers.