That aside, limiting the group to 4 feels painfully restrictive not just when it comesto narrative/dialogues/cross party interactions etc, but even in gameplay/mechanical terms. Picking roles, taking advantage of all the rewards offered by the game, etc. You either make an active effort to make sure your four guys cover the most different basis in every possible way with virtually no overlap (which also means "fuck you" to most "hybrid roles" and exotic less-than-overtuned classes) or you'll end with ton of equipment unused, class-specific quests not explored, etc, etc.
I mean, as an example above all: let's say I want to play a class X which is already covered by a companion I like. I couild consider to double that role with some minor differences in specialization for a larger party, but with four slot included mine? I ether reduce the range of my party capabilities even more drastically or I'm basically forced to excluded that companion as a viable option.
Ok, in your personal opinion, how much content should you be able to experience on your first playthrough?