Definitely.  I'd hesitate to take on more than 10 people.  That said, I also hesitate to take on too few.  Like I mentioned in the OP, I expect a lot of player-driven content between Main Plot Points.  If the players choose to just breeze through the main story and be purely reactive to the narrative, that's fine, but I would hope that people would be excited to make this game their own in a sense, and introduce subplots of their own to add to the action and development.

tl;dr: More is good :D