I do have to say I love the beta so far. The changes seem natural and not overly forced. I do wonder about replay-ability with the current stack of characters. Having 6 characters in PoE made the game ultimately re playable to a point that I'm still starting over with console built characters from the beginning, etc. I do love that the console is available on Deadfire, but I didn't see the all too important (end game feature) of building out ultimate builds to 'cheat' your way through the game on whatever difficulty with whatever build you wanted.
...all that to say- 5 characters probably