The only way to make fair to investors is to pull the random number from a provable RNG such as a hardware one. Services such as random.org offer this. Of course, this translate CP risk from the OP now to a different 3rd party. Also, you would not have the standard type of provable fairness, though any player could audit random.org (or any other true RNG service) to prove the #s are fair to the player in that way. I think that would satisfy most players. Not sure if more investors would prefer blinding the OP to the random numbers but transferring it to a 3rd party.
This would be worse than the current setup: without provable fairness, anyone with access to the server could slip in a number and you'd have no way of knowing that number wasn't chosen specifically to make you lose. The concept of "provable fairness" is actually a pretty genius innovation. Now the idea is to extend the concept somehow to protect investors as such as those in this site.
EDIT: Reduced length of quote above.