The most importand thing we want to do in future giveaways, is that everyone should have a chance of winning. Also the people that don't have alot of btc.
Cryptasm
You could do it like this: let's say the idea is "lowest odds of getting a specific streak" (so not longest streak, but least-likely streak w odds between 50-90.) Normally a site would say "min x avg bet", but you could say: "max 2 BTC prize, you get 1000x of your avg bet". So if the least-likely streak has an avg bet of 0.0008, the prize for first would be 0.8 BTC. Then the second least likely is 0.0006, gets 0.6 BTC. ETC. till the 2 BTC is finished.
However if you would do anything with a streak etc. imo you do need to:
1) Make a live-updating leaderboard tab which also show the potential amounts the persons would win if it ends now.
2) Make a live-countdown on that tab to make sure everyone understands the deadline.
3) Don't use my example amounts/numbers, I am just guessing, I have no idea if "avg bet" is a good use too. It might be bad because after a long streak people would just bet really big to make the avg much higher and still win all the prize. It was just an example of how to potentially share the amount fairly among big and smaller players. With the streak idea that is actually relatively more difficult tho.