The thing I need to see before I decide on my build is how quickly these lists can get hellbent. I played a Rakdos suicide deck a ton before Kaladesh, and it was one of the strongest decks I played with at the time.
Olivia's Dragoon was so important to that deck because it allowed me to get hellbent on demand. This matters when you want to turn on Prototypes or Priests T3 or T4 because you're trying to end it T5. I also used to run
Ghirapur Orrery that I wanted to turn on asap in games that needed it, and while I don't think I'd want to run that now, we've got things like Hazoret or Neheb (or Strider I guess, if you're into trying that) that you want to make sure they can do The Lord's Work when they drop.
You'll get those draws where you start with 3 lands and think you're fine but then start flooding out, not being able to play more than 1 per turn and keeping you off hellbent. An unconditional discard outlet is very nice then. I can't help feeling that a deck looking to get hellbent wants something like that.
Attacking for 2 in the air makes a difference too. Sure we have Copters and Harvesters around that didn't exist when I was doing it - but really, what opponent isn't going to be attacking with them thinking they can race your ass instead of leaving them back to block? At least until this deck proves to everyone on the ladder that it races harder.
No, you won't want to pitch a bunch of cards on the spot every game. You'll have draws where you curve out perfectly and won't need more discard than the various 1-off options. But you'll also have games where you don't and need to turn your **** on before your opp can stabilize and put the game out of your aggressive reach.
So the questions I want answered once we can play with the new stuff are: 1) how reliably can we get hellbent? And 2) how much do some of the new cards add to the strategy's ability to survive and compete if the game starts going longer than T5 if not getting hellbent?