Reducing group size is definitely an option.  In my head the ideal size of the group would be 6 people, but perhaps limiting it to 4 or 5 would be a better idea.  

An RP like this could have more than one 'round' of play if enough people show interest.  Perhaps doing an initial run with a smaller group of people while increasing the amount of trials would be sound.  It'd help everyone get into the groove of things and give me a chance to work out any kinks. 

Of course that all depends on whether or not the idea catches on, so that's a wait-and-see kinda thing.