I have to agree with LordCrash on this topic.
Another problem with the "every companion is a protagonist" solution that really pisses me of are the forced conversations. Sometimes there are conversations that start automaticly after a fight or when a npc aproaches you by himself or something like that. And most of the time I don't have any control which of my characters will get into the dialogue. Mostly it is just the one who is nearest to the npc. Then I have to talk through this conversation with a character I don't want to. I want to do all these important dialogues with my main character.