The problem is.. how does a reduction in resources make sense? You break the treaty and lose money/food.. It doesn't quite follow.
A treaty is a social/legal agreement and as such, there should be social/legal consequences to breaking it. How about, if you break such a treaty - then you lose combat protection (in whatever form it exists in-game) for 12 hours. (time logged in, not real-world time.)
Basically, you break the other treaty so everyone is ticked at you and can attack you without any limitation to the number of times. Thus - you wouldn't want to break a treaty unless you were in a very strong position and very confident of your ability to withstand your enemy and his friends. Additionally, I think that any peace treaty would have to have a time-limit. For instance, treaties could be make which last 1 week, 2 weeks, or 1 month in real time.
"He uttered the word of curse, crush him with our Orcish iron!"