As long as a trusted escrow is receiving/holding the money it I'm in for a traditional bracket and squares.  I think a confidence pick em is good, but it would need to be for every day and that's a lot to keep up with for everyone involved.  Same with a survivor, it takes a ton of planning and everyone needs to check in pretty much every day which is going to be tough for some people.

I have experience running both brackets and March Madness squares so I can assist with the set up and can let you know what kind of payout structures work for ones I've held before.  Again, assuming we can get an escrow to take/hold/payout the funds.