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We don't need a separate jackpot pool, it's a regular bet, with a regular 1% house edge, and so the investors will bankroll it just like they bankroll every other bet.
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that is the most elegant solution so far in my opinion!
(assumed that you find a way to implement this without cluttering up the beautiful, simple just-dice user interface)
I've been thinking for a while about having a way for players to make arbitrary numbers of bets at a time on a single roll, for example:
90% of stake at 49.5% (50.5000 - 99.9999)
9% of stake at 10% (90.0000 - 99.9999) -- note the range overlaps the previous bet - rolling 95 makes both the these bets win
0.9% of stake at 1% (30.0000 - 30.9999) -- note it's a mid-range bet
0.1% of stake at 0.001% (0.0000 - 0.0009)
Currently a bet is defined by 3 things: (stake, chance, hi) - ie. the amount to bet, the chance of winning, and whether to bet hi or lo.
The idea is that a bet evolves to become (stake, [(share, chance, hi), ...]) - ie. the amount to bet, and a list of (share, chance, from) triples, where the shares sum to 100%, and each 'from' is the low end of the target range; ranges can 'wrap around', so (10, 20, 90) means to bet 10% of the stake at 20% chance, where rolling 90-99.9999 or 0-9.9999 wins.
That allows this 'jackpot' style bet, where 99% goes to the main bet and 1% goes to a very low change, high multiplier bet. It also allows more of the "slot machine" style bet, where you have a range of different possible payouts with increasing payouts having decreasing chances of happening.
The tricky part is in deciding how to present this to the player. It's far too much for most people to want to have to look at or think about. I'm guessing we start with a few preset bets of this type - maybe just the 'jackpot' one, and later add a 'bet editor' page to allow those who want to to define their own custom bets.
