Home Prices

I think that there might be an interesting opportunity for predication markets on various home price indices. The underlying market is huge (>$10 Trillion), homeowners are still licking their losses from 2007-08, and there don’t seem to be many organized products.
The one exception to the above is work that I do as market maker for the CME in the Case Shiller home price futures. However those contracts only cover certain regions for certain defined horizons. I’d imagine that there might interest from people looking to hedge the value of their own local area. Any such contract done OTC introduces counterparty risk, I’m here to learn how that can be addressed with Gnosis.
I’m brand new to Gnosis and would need to get up the learning curve in how markets work. Are they just binary with fixed payouts? Can there be variable payouts subject to a cap on either side? or, (a version of the last) can one structure an option where payout is measured by a set of “if…then” statements relative to published index.
Looking to learn and give some of my prospective clients comfort in counterparty risk.