Sometimes in Dom I, I noticed that the supply in a province would suddenly and inexplibably drop, causing starvation. The next turn, it would go back to where it had been. I figured there was a stealth army passing by, and they ate first, but I'm not sure.
I think that "Survival" skills should allow half-supply usage in the specific terrain, in addition to a reduced risk of starving. And, if stealth units have to become a little more pricey to compensate for the fact that they don't ever starve, then so be it... because that's a strange game mechanic
Oh, and the suggestion about a stealth boost from survival is also a good idea. Possibly, survival could even give a terrain-specific stealth...
-Cherry