Why not try to set up a group using this medium or similar. Many, including me, have done it before. Pick dates and a base then stick a post in the open invites section.
Prebook 3 or 4 rooms in a hotel and have a cut off date where you cancel any unbooked rooms, giving the hotelier a month or so to rebook. Many places will not need a payment up front if you use booking.com
If you get some interest plot some routes or set up a Facebook group and let others do the donkey work.
I have stopped doing this sort of thing as I now have a group of 20 or so in a Facebook group and we go on a trip each June. 12 rocked up one year but more usually its 6-8.