Just a way I think this could be handled well. Let the player bet X amount on themselves, with a cap of, say, 500(x) brains = X, with x being their purchased rank. Each rank one add become x+1, so each new rank you buy let's you bet another 500 brains on yourself.
Now, have 2 different ways bets are handled. Either make it so everytime you kill someone else, give 7% of their betted amounts as brains to them. This % would go down the higher rank you are, so a Hero would be getting only 4% of their bet as brains or such. If it's a juggernaut round and your the juggernaut, make the percentage closer to 2% to start, so our Hero would be getting .5% of their bet as brains for jug kills.
The other way, is make a bet you will survive/get most kills as dark hunter. This would give your bet * 1.1 back to you. Any kills gotten as a survivor will give you the normal brain amount, but nothing extra. Any kills as a dark hunter will get normal brain amount, unless you are also the top hunter, which will give your bet * 1.1 back. If your the juggernaut, your money back if you survive would be reduced to 1.05 * bet.
Also, whenever someone quit, their bet would be lost. Any bet already paid out would not be lost (say they disconnected after getting 200 brains from a kill bet), but the rest would be forfeit. Any time someone bet on themselves, it would show the server and amounts, and killing someone would give you .25 of their bet.
This way keeps a incentive for survivors/hunters to bet on themselves, while keeping it mostly safe from people cheating. It also let's people know who will give the most brains to kill.
