Another World Tier would be ideal to make the 80-100 gap not feel so shitty.
A horde mode/boss rush game type like Halls of Torment or Vampire Survivors. Give me upgrades that only work for the run, but as you kill more and more you get some kind of currency that can be used to purchase permanent gear for your character. I guess it's just Helltides with ramping difficulty and density.
Paladin/crusader is a must at this point. I've missed monk from D3 and hope it returns at some point. I'd like for them to make some kind of turret building/tinker class fit thematically. Give me bombs and junk!