As long as you are happy to handle a nine player rotation, I guess it's no problem for me. The only concern is the length of time between each player's turns - if it gets too long then players can (a) forget they are supposed to be part of the team and (b) lose track of what the game is all about and what the team strategy is. If your team runs a 72 hour rotation then it will be almost a month from one player's turns to their next, and some teams struggle even to do 72 hours. As long as you believe you can maintain momentum with nine players then, fine, go ahead.