I'd love to see more races and classes. Artificers, Tortles, Warforged, Tabaxi, etc. There's a bunch of missing subclasses too, like Storm Barbarian or Swashbuckler Rogue.
Maybe mod tools would allow that, but at the same time I'm not convinced. It just seems like easy territory for an expansion, sort of like Tasha's or Eberron... but for the video game.
No idea, sorry, I didn't play Early Access. I'm still waiting for some to get updated for the build I want to play to work (Shadow Blade user twinning Booming Blade cantrips).
I might just tough I out and play vanilla for the first playthrough, anyway.