Deprived,
They would not know the server seed, so that would not be a vulnerability. There would be the client seed, server seed and then the server seed would be hashed using a random number generated by random.org. This would make the game provably fair to investors. There are many proven true random # generator sites out there besides random.org also
It wouldn't change anything. Dooglus could just request a random number from random.org then change his bet size once he calculated what the result was. And that's IF there was some way of proving which random number was used for which bet. It adds complexity but no solution.
EDIT: If your concern is trusting dooglus then you can't trust ANY server logs or similar he has access to. That's what makes the problem (if it is one) very hard to solve.