We will find out the answer to all these questions, eventually. They are good ones, so hopefully Larian is listening if they haven’t already thought up solutions.
Personally I don’t think I’ve ever had a companion in a game that I initially liked but eventually grew tired of, but that seems like a reasonable possibility.
We know that if nothing else you will be able to add custom characters, though that isn’t a sufficient substitution for most people. Hopefully the characters are all written well enough that none of this should be an issue.
But it shouldn't be an issue. If character arcs are developed well through the entire campaign, you will want to do several playthroughs to see them all. Good replayability here.
