I think this is a really bad idea because it adds too much randomness to the game--you won't know if your opponent will be cashing in a small amount or very large amount of armies. More randomness == less strategy.
I think a much better idea for an alternate spoils is to use the currency method (stars on a card) which is used in modern versions of the Risk board game. It has some of the same advantages of poker method (it lets you cash in with any amount of cards; it also allows for some randomness because you don't know how many stars you will get per card). Its advantages are that it's more simple (no having to know poker hands) and is established as a workable game mechanic.http://en.wikipedia.org/wiki/Risk_%28ga ... n-in_rules
You can say "if you don't like it, don't play it" but the reality is that there can only be so many options for games before there are too many. We should go with a method that's been tried and true and not have endless options for spoils.