I think it's a cool idea with some potential
The site will also be monetized with ads. The profits of which will go towards purchasing more coins to offer more contracts.
Think you'll generate enough traffic to pay the interest? You probably will anyway. I just worry that if I sign up and deposit some coins, you'll get just 2 chances to show me ads, 60 days apart. I might drop by more often if this was coupled with something else interesting: games, articles, commentary, a trollbox at the very least

Oh and one more thing, the troll box is a possibility, could be a good gauge on how people are liking the service and a place to maybe get some suggestions. Maybe we would have the first chat box rather than a troll box though? :p