Yes, I think this is possible because the documentation for the Game Kit Programming Guide (ad hoc connection section) says:
The maximum size of a client-server game is 16 players.
Your biggest problem will be how to get all the players to connect together (I would go to PeerPicker - do not use your own version of the user interface, because it is very painful to execute it correctly, especially for so many players)
Another problem you may encounter is that bluetooth may not be able to send and receive data fast enough for 16 players (I think 16 players deal with turn-based games)
Good luck;)
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