I really would hate it, If they kill off every character not in the Party. Is that already a given or an assumption based in DOS 2?
As for party size: I'm with Tuco and Niara, it should be a party of 6. D&D has so many classes and possibilities, that limiting oneself to four characters only feels crippling. Plus it's tradition in the BG franchise to have 6 partymembers.
