I have heard on both Fextralife and Wolfheart recaps of the private content creator preview that all companions can be fully reclassed.
Since this is optional, its completely up to you if Wyll, Gale, or Shadowhearts’ classes don’t match their stories. I think this is the right design choice. I won’t change any character with a class intrinsic to their background, but for players who don’t care about the dissonance, why not just give them that option? It isn’t costing anybody anything.
Even for those you could argue for class swapping, if only maybe at diffrent points
Mizora now seems to be more of the traditional patron and if will fully escapes her it'd make sense for him to lose his warlock level and put them into bard or something.
Shadowheart clearly isn't a proper Shar cleric and exhibits traits of being a sorcerer
Gale even makes sense as a wild magic sorcerer woth his chest thing
