I'll be happy with a Core Rules difficulty where the game plays exactly like 5e.
I'd like a good tactical challenge but through resource management / rest restrictions and removing easy cheese like "help". NOT through pumped enemy stats. I'm ok with more enemies but not enemies that have 50% more HP and deal 50% more damage or whatever nonsense like that.
Also not a fan of delving through a million toggles of game settings and having to make my own difficulty. "Core Rules" should be simple enough.