Better to make a mistake here, among friends, than in the real world.
I think they could easily massage Minsc into the group: being turned into a statue did it, or the tadpole did it, etc. As for tone, well I remember speculating that being implanted might have cured his brain damage, but even if it didn't Minsc wasn't exactly 'on book' in the other games either, so I'd probably still be able to roll with it.
Does having to choose a companion solely for metagaming purposes, qualify as ludo-narrative dissonance. I haven't played with Astarion for a number of my last runs, and even without Shadowheart, I don't think I lost out on anything. There's always a key, or a platforming side entrance for the locked doors. The only times I've actually been locked out of something, is if every party member whiffed a perception check.
