Okay, that's an interesting idea; a totally pull driven economy. All the base resources are harvested and accumulated locally, and only actually shipped when a build order in some town requires them. The time to build in a given town now includes the time to transport the goods, as climber has mapped out. When you design a new unit, then, it pulls both NR and MR from wherever is closest to start building your unit. Would towns that have intermediate MR then accumulate them like an NR would?
As an example, suppose you build some arrow +2 (I'm getting bored with swords) using a fletcher in town A. The fletcher requires wood, iron, and potions. The potions have to be supplied from an alchemist in Town B, and iron from a smelter in town C. Town B's been getting crystal from a crystal mine near it, and has accumulated 10 potion +2 in it's alchemist shop, but the smelter in town C just finished sending halberds to another town, and is fresh out of ore. The order goes out for 20 arrow +2. The AI has to then understand that it needs to get 20 ore from a mine, ship it to town C, have it made to iron, then send the 20 iron to town A. Meanwhile, 10 more crystal needs to leave the crystal mine (let's suppose it had that in it's local reserve) to town B to be made into 10 more potions. Do 10 potions leave town B immediately on a caravan, with 10 more to come later? Or does town B's alchemist wait until it can fulfill the entire order of town A's before it ships? I don't think I like the idea of an unlimited MR conversion rate in any factory, Climber, though I see the point of it. All of your time delay comes from transport, not conversion of goods. Having an infinite MR conversion rate on factories, though, removes some of the strategic choice for more factories of a given type in a town (with it's itinerant use of land, since that's a limited resource as well). With unlimited MR, I'd just put all the necessary factories in the same town, and have the NR shipped there continually.
I think we've got to resolve this issue of obsolescence that's been raised, too. While I'm building arrow +2, I research tech that opens up arrow +3. Do I need to start over again, or can I just ship the tech necessary for the upgrade (potion +3) to the town where the archers +2 are? I think that's a better answer. Provided my archers are in a town where archers can be made (a fletcher is in the town, in this case), I can click on them and upgrade them the same way I could build new, but less materials are needed. Eventually, of course, my iron, wood, and potion +2 will be replaced by adamantium, bone, and potions +5, so there's not necessarily any benefit to upgrading that just building fresh wouldn't get you, apart from the population use. If population is easy to come by (there was a dev post saying towns might range from 100 to 1,000,000 population), then there's no incentive to upgrade if the upgrade is technologically complete. What that argues for is that those times when a complete technology upgrade (arrowhead, shaft, and magic) can be available should be rare. The alternative, from a balance standpoint, should be that the time to ship upgraded MR should be short relative to the time required to train new recruits. This is the other reason that infinite MR conversion rate may not be the best; it acts contrary to this requirement. An upgrade of tech shouldn't require training time, and if training is long time relative to the shipping time for upgrades, there's an advantage to upgrade vs. build fresh. From this argument, I think it might be better to have shipping times short (relatively, and improved by roads), and MR conversion times in towns be long (again, relatively).
If, however, you're balanced so fresh builds of upgrades are preferred, we still need to do something with the obsolete builds. Returning them to raw resources is probably the best way to handle this, so that they can be drawn upon again when a new build order comes available.
So, stocks of all 20+NR and 200+MR in each town. You should be able to sell "obsolete" resources to the merchant to convert them into gold (you won't use iron again once adamantium becomes available, so dump your old stocks on the merchant). NR nodes need to be upgradable for both production and resource, or else that big, well developed iron ore mine deep in your territory will be less technologically useful at the end than the new adamantium ore mine. It essentially becomes a profit "gold" mine, as you'll sell all the ore to the merchant directly from the mine. Or, maybe you force us to caravan it to a town before we can dump it on the merchant. Build orders for new units automatically draw their NR and MR from whatever stocks are closest, whether in the town itself, or in a close by town. The caravans carry exactly what is needed to meet that specific order build in that specific town.
We're gonna need a good UI to be able to watch what caravans are moving what NR and MR to each town to meet each build. And we still haven't resolved the issue of a technology upgrade that occurs (potion +3) while an old technology is en route to a town (a caravan carrying potion +2).
Thanks for the Karma, Climber! Uh...what...er, what is that, exactly? I'm kind of a forum idiot, you see.