Mulligans
Aggro Mulligans
without frostbolt/other early game, these are pretty much your only anti-aggro tools before your board clears come live on 6. Messenger Raven is the weakest keep here, I just listed it bc it's cheap.
Midrange Mulligans
Probly gonna struggle here. There's not a lot of healing and the board clears don't go very tall. Not sure what you need to make it tbh.
Control Mulligans
It's not clear yet what the most powerful tools are, so idk if Malacrass/Power of Creation/Jan'alai are reasonable keeps. But these legendaries definitely give some absurd value that you don't want miss in Control mirrors.
Depending on what the meta looks like, a second Rotten Applebaum might be better than Archmage Vargoth. Archmage Vargoth is insane when it sticks and you get to cast double Power of Creation or Flamestrike. It’s even powerful to play double Arcane Intellect on 7 in control mirrors; but it’s pretty unreliable with Polymorph and Conjurer's Calling.
I can’t tell if I like Arcane Intellect. It works with the controlling/value plan, but it’s mostly there to juice Astromancer, which probably isn’t a good enough reason. Possibly should be replaced with Frostbolt to fair better in the early game.
There might be a home for Pyromaniac in this list bc drawing is good with the controlling plan, but it’s usually only good with Daring Fire-Eater, which seems too weak.