If a new guy is good enough he can make new rules. If they are "better" than the old rules go with it. Then again, what do the audiences think of this new direction? Is it working? If it is then my instinct would be to go with it.
IMO it doesn't matter who's calling the shots. . . . as long as they are good shots. This is always going to be the problem facing the "fun" player who wants to play some of their "favourite" tunes with some "mates". You can't leave every band when you run into something that you don't like, cos there's always [i]something[/i] not to like! I never want to play my favourite numbers in bands. That way I'm never upset when they mess them up or fed up when they drop them.
Never mind what it was, is this a good band now, with good players? I'd stick around.