That's good, but I suspect continual monitoring of headline markets ("who will win the US Election") is insufficient because FB is big enough to influence the result.
What are you going to do if (when) you detect manipulation? You won't be able to take it offline without the President using it as an example of "liberal bias", and you won't be able to ban users because of the same thing.
I know you won't do this, but I think you should experiment with some lower-stake markets first, and potentially use participation in those as a gate to the high stakes markets.