This have to be super-rare (impossible to buy for example, but can be earned as a prize in events) coupon, that is hidden from everyone in inventory and transaction history. The usage is simple - /safebet 500000 example. In every case, both if you won the bet or not, the coupon disappears. No one can see that bet is safe till the game is over.
* If you lost the bet, there's a message appears "X saved the bet with a coupon", no one got X's money. he does not loses them
* if you win the bet, you win the bet.

For example, there is 4 betters. X safebets 500k on 1, B bets 100k on 1, C and Z bets 300k on 2 both
If 2 wins 1, C and Z splits only 100k from B bet, but not X's 500k