One idea we were floating around was the Civilization model. If your realm has a region that makes wood, then you whole realm is considered to be supplied with wood. This also makes some regions more strategically valuable.
Ooh, I like the sound of that. One suggestion I'd like to make is that rather than automatically supplying the realm with wood, the woodlands lord puts his wood on the market for X gold/day for Y days and a King (or equivalent) would purchase access to it wood for the duration (like in Civ 5 where you can sell a resource to the AI for 30 turns and in exchange get either a lump sum, gold/turn or a resource back), which *then* supplies his/her realm with wood. This would make resource-producing areas (woodlands in this example) more desirable for lordships since it would increase the money they bring in; and, a realm with 4 woodland regions would then be a major exporter of wood and bring in significant revenue that way, while the regions are still desirable since your benefit (access to wood) depends on the good graces of your neighbor who controls all of it.
