Those sound like good general ideas for the regular islands.
Having to build marketplaces everywhere is a bit of a bitch. Also, it seems a bit, I don't know, half-hearted? Ineffectual? It's trivially easy to circumvent by just posting orders the opposite way, and having the other region post an offer the lord/steward/banker can accept on behalf of the region that doesn't have a marketplace. IOW, the only thing this would affect is the visibility of automatic orders. So long as the region's lord, the region's steward, or the realm's banker are available to do the trade, the marketplace restriction is irrelevant. So, why bother?
One idea to deal with looting might be to completely disable trades into or out of a region that is occupied by enemy soldiers that are actively looting the warehouses. Or maybe have a chance for shipments in or out of the region to be intercepted based on how many enemy soldiers are in the region. That would be a nice bonus plan. The banker tries to shift 1000 bushels of food out of the occupied region, and it gets intercepted and stolen by the invaders.
For the war islands, I think we should go even further, and just abstract food to the point where you don't need to manage it at all. So long as your realm produces enough food, everyone is automatically fed. When you start running short, regions start to suffer. How much each region suffers should be based on how much food they produce vs. how much they need. Regions that produce a surplus should never suffer, barring looting. Regions that have a 75% shortage should suffer more than regions that have a 25% shortage.
Looting food away from a region can be figured in by reducing the region's production, and therefore how much food is produced that day. Looting the other way, stealing food to feed yourself, is just lumped in as extra production for your own realm on the next day. Seems like it shouldn't be too hard to come up with some kind of system to support this. It allows food to still be important, but completely removes the need for people to actually *manage* it.
