It seems like this would create an incentive to keep your coins in an huge number of wallets, so when you get randomly picked you only lose a small fraction of your value.
I don't think having users spread coins between hundreds of wallets is your intention.
You could do that, but in the long run it wouldn't make much difference. All it would do is decrease the chances that you would lose all of your coins at once.
One downside would be that if this occurred on a mass level, the whole idea might become pointless. Let's say someone had 100 wallets. At a 5% decay rate per month, you could expect that, on average, 5 wallets would be selected for decay. In this case, the "gamble" becomes predictable.
In other words, it would likely turn into a coin where people simply lose 5% of their current holdings every month.
Almost sounds like the Occcu
Occcu = GambleCoin?