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It needs to work something like this:
- 1) Everyone who wants to participate should not have any control over the 500 SPR anymore. He can't even take the money back.
He can just prove later that he has control over the address he used to pay the 500 SPR. - 2) Everybody will have to pay that amount into the same SPR address, called the jackpot address, so that everybody can see at all times how big the jackpot is at the moment. (this will help get more people on board the juicier the jackpot looks)
Preferably NO human being is in control of this jackpot address. (So this must be some sort of scripted address whose private key is never known to anybody (its creation was merely triggered by a dev), and this scripted address somehow waits for somekind of event to be triggered. 
)
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Ah, ok. I think this is my bad.
Having to send 500 SPR to an address and not being able to get access to it again, plus having the built up funds used to create a payout, that's a lottery. We can't do that:
According to 12 USCS § 25a , “lottery" includes any arrangement whereby three or more persons (the "participants") advance money or credit to another in exchange for the possibility or expectation that one or more but not all of the participants (the "winners") will receive by reason of their advances more than the amounts they have advanced, the identity of the winners being determined by any means
By asking people to put aside their coins to participate, they keep control of their money. They can take the money out at any stage, but then they are out of the game, even if they find the van gen. We cannot ask people to pay 500 SPR to build up the prize fund, but we can ask them to put them up as collateral, but they have 100% control at all times.
My suggestion relies on some of the game theories of lotteries, but it is not a lottery. The coinbase is used to build up the stake, in BTC. If its in SPR, no one will participate.
The few miners we have at the moment won't care about losing 1%.
The higher the build-up of BTC funds from the coinbase, the more people will want to play. You are using 1% of the coinbase for x period of time, to generate demand for SPR, and you are doing it ahead of ServiceNodes coming on stream.
The maths behind finding private keys means that someone will find the winning address if the public key is short enough that it can be found in a reasonable time. What that reasonable time is, is one of the questions.
