Yeah, BP didn't really branch out, but did include builds with cutting-edge features it needed, but that were not even stable enough for nightlies (at least in theory. I was using BP builds all the time, they were rather reliable). In fact, they were no different from test builds posed on this board, except for the more prompt update schedule and the fact they sometimes contained multiple unstable features at a time. It was something like Antipodes on steroids.
I think that here, branching is a bad idea. It adds a lot of overhead to manage yet another code branch, especially one that is not planned to be merged in at any point. Inferno was rather unproblematic, because the difference wasn't too drastic, and didn't affect key areas of the game like this one would.