Glad to know you've been hitting the same roadblocks as I have. I'd love to figure out how to create a system that's provably fair, for players and investors, real time, and trustless. Not sure if it's possible though...
My intuition is that it's possible, just not really practical. I think the way could be to have clients bet with the game server via a trustless payment channel (this whole thing is a big giant ball of complexity, and greatly limited by bitcoins script system, but 50% bets are pretty conceptually easy to support). Then the game server also has 1 payment channels open with each investor. So effectively each investor is running their own seed server, and gets each bet.
The main issue is that there is a crazy amount of edge cases, some of them that really affect the user experience (e.g. if 1 of N investors don't reveal their seed, the bet will have to stall until some timeout period which is probably measured in hours or days).
But frankly, I'm not really sure it's worthwhile focusing too much on investors. I think the bustadice scheme is probably "good enough", and doesn't open a giant pandora's box of complexity.
What I think is an area that could benefit a lot more, is improving player guarantees. Provably fair is obviously good, but I don't think it's nearly good enough. =] If you weren't cheated, it's easy to check. But it still requires checking. And let's say you *were* cheated, you have absolutely no proof (non-repudiation). And furthermore there's no protections against an operator simply stealing your money.
When I get some more free time (i.e. after bustabit v2) I'd like to experiment with the idea of generating all user deposit address in a bidirectional payment channel. And you only release your funds 1 bet at a time (i.e. it would be impossible for the site to exit scam).