A signed message from an address containing the coins?
Furthermore, what system is in place to ensure that the coins remain in that address?
I think you're missing the point. I don't care if they really have the coins they claim to have or not. I let them risk 1% of their total claimed amount, until the coins I have control of from them are less than 1% of the total they claim. Then I force-divest them.
It could be that they have in fact invested all their coins, and the other 99% in the "local" storage are a lie. That just means that they're risking 100% of their coins per roll, and will go bust when the first max bet wins.
I don't think this passes any extra risk onto other investors. It is somewhat like trading on margin, but with the important difference that there's no risk of slippage when I have to "liquidate" their position. I just remove them from the bankroll.
The effect I'm looking for is a way that people can risk more than 1% of what they've sent me without making the calculations too complex. I think this "fractional reserve" idea does it. Please don't just react to the fractional reserve concept at a gut level. I don't need to be holding all the coins you claim to be risking 1% of (and I don't even care whether you have them either), so long as I always make sure I have access to all the coins you're actually risking per roll.
Well then forget about the local coins completely, they are totally irrelevant.
What you are trying to do is simply a more computationally efficient way to get arbitrarily increased risk exposure, right?
A person has a deposit amount and a coin multiplier amount. Right now the multiplier is 1. You track real coins on deposit, and multiplied coins. If a loss on an account holder's multiplied coins exceeds the balance, then the real balance is wiped out.
It's clever, but I suspect implementing it will be less efficient than you think. You need to track two balances per account. You need to test for the edge cases for when the loss exposure on a bet would potentially exceed the remaining reserve of some account. What do you do then? Force liquidate or lock account when reserves are less than the potential max loss from a single bet?
Yeah there's some issues with implementation of it. And some potential interesting things investors can do - such as when a whale's betting big run a martingale against them by modifying their local coins balance (if you remember I mentioned this ages back). Also a large investor can try to freeze nearly everyone else out when there's no whales around by inserting a large local value so that max-bet rises to where anyone operating at 10% with 10% of coins deposited can no longer cover a single max-bet so is frozen out of taking the low-level action. As soon as a few start doing that everyone who wants any action when whales aren't around ends up having to deposit all coins anyway.
Other issue with it it transparency. If someone's balance is near the max-bet then they'd be in and out of investing a lot if there was a whale betting. It would be hard for them to verify that their ending balance was actually fair. The lack of ability to easily see that your balance was what it should be in those circumstances is possibly the largest argument against it from an investor's perspective.