Devs need to learn to not try to please everyone.
Respecing written companions to everyone's favourite class just ends up watering it down for everyone.
If I turn Astarion into a wizard, how does this affect you?
I think it's more to do with how does this affect the personality of a character that is now a main character. Right now, the characters have established a strong alignment with their role. Their personalities in my opinion fit that role. Let's guess what would happen if Astarion was a wizard. My guess is that the range of possible stories for Asterion as a character become more limited to accomodate this feature (like it was in DOS 2 , I had very limited side quests or background knowledge of my companions and I wanted to learn more)