We would need a total of 8 players. If we had 6 or 7 I could fill in the missing characters.
The GM(s) would also run the NPCs, canon characters and villains (such as BPO) though I suspect there would be room for a PC villain along the way.
Each of the 8 in the main cluster we would be following in the story the others are in. Although they wouldn't be physically present, they could experience what the other's do and be present in spirit, helping out with their own unique skills. We would need a separate game thread for the physical storyline of each character and as GM I would cycle through everyone's threads and build a larger story that connects them together through events.