I agree with the OP. Even the ability to have extra levels for multiclassing, and to gain higher-level spell slots (for upcasting spells, metamagic, etc) would be a welcome addition.
While I've used mods in plenty of other games, they feel a lot more problematic in BG3 so far. While I couldn't care less about the achievements, the non-graceful way in which mod failures/removals affect save games is an unacceptable risk for a game that takes so much of a time investment. Perhaps if BG3 included an internal mod manager like say Unreal Tournament from 20+ years ago, or Conan Exiles from 5 years ago, it would be a bit less cumbersome. Also, if modlists could be loaded dynamically based upon what's in-use for a particular save file that would also help -- having to juggle them when going between different multiplayer groups and solo saves is a non-starter for me.
Also what's up with the BadWrongFun arguments about people playing the game too much? "How dare you become engrossed in a gigantic game with an overwhelming amount of content? How dare you want to experience it all?" Just because some people can clear all 3 acts in 60 hours does not mean that's "normal". Reddit, Facebook, forums, etc. are full of reports of people taking far longer than that to clear even Act 1.
Anyway, if the way over-leveling was handled in the mod was an option that could be enabled in the core game, you'd have my vote for including it.
