Such a long thread, I even don't know wether I posted sometimes or not.
For me it's easy, I like 4 person parties and I hope it stays as it is. I don't care at all for tabletop here because there usually a char is played by a person, but in the video game you have to play all the party members. I find it utterly annoying to do so in Pathfinder turn based for example. As BG 3 (thankfully) is turn-based-only, a party bigger that 4 is a nightmare for me. Ok, I'm exaggerating. It wouldn't be as bad as in Pathfinder with it's stupid 3.5e or so rules, but bad enough.
Okay, so play your game with 4. I'm not trying to stop you from doing that. So why are you trying to stop me from playing with 6?