Whatever they were to add, it'd need to be some kind of 'impending doom' threat to everyone in the party for some of the current companions to be willing to work together. Or they would indeed have to rewrite them completely, and then they couldn't be written to be at odds quite as much which would just lead to a boring cast of characters.
Plenty of other ways to make that stuff work, that said, it's much too late now to overhaul part of the game to such a degree - hell, even the first Early Access build was probably too late.
