Here is the thing: That is an unreasonable request, because the characters have specific dialogue, quests, backstory etc. !
Changing their class wouldn't make any sense.
You also need to keep in mind that larian will at least double the current amount of companions until release, so the "who am I supposed to bring as a ... ?" question will become irrelevant.
Ofc it isn't ideal right now, but changing something fundamental about how companions work based on a problem that will be fixed sooner or later anyway is a terrible idea.
The only thing I could imagine in the final game would be a respec option that resets a character to the first level, but doesn't allow you to change to a new class. This way you can correct mistakes you made when leveling up, but won't be able to suddenly play someone else...
