I must somewhat dissagree with the idea of artificaly splitting up the market for any given class of goods. It would simply dillute the number of users, thus huring the liquidity of the whole operation, which is going to be the major sticking point in the whole operation. As many users as possible should be using same market, to ensure that the market remains fluid.
Well, first, I agree that we shouldn't artificially split up the market. And, well, we wouldn't be -- players would, obviously, if they so choose.
I think that this really relates to market entry and accessibility, not to mention playerbase size. First, if we allow markets to be closed, then that is the ultimate barrier to entry -- no competition. Additionally, the liquidity of that market would obviously decrease, as it would be inaccessible to a number of potential sellers and buyers. With that thought, perhaps the accessibility of the market should be separate for buying and for selling; that is, perhaps there should be an option to allow countries to buy from the market, but not sell. Thus, there will be available buyers to accommodate the sellers. Of course, without many sellers, there would be low market depth, prices would rise, and goods may even become unavailable: the problem you were noting in regards to market liquidity. However, this seems relative to size: if there are ten buyers and ten sellers, then the market depth is equal to there being one hundred buyers and one hundred sellers. Of course, the smaller the playerbase, the more influence any given buyer and seller can have on the market.
This all is getting beyond my area of knowledge, however, so consider your opinions as valid as mine. I guess my thinking is that individual markets will be adjusted to accommodate buyers. I would think that markets would be created as they were demanded, rather than in excess, because an unused market would obviously be of no use to its creator. Likewise, to ensure this, perhaps there should be a cost to opening-up and/or maintaining a market. This way, hopefully the creation of markets would follow demand, and should there be enough demand to integrate markets, this should be able to happen.
Also, it might have been mentioned elsewhere, but even if one doesn't belong to a given market whatsoever, prices and amounts should still be listed: this would keep competition more stiff and information more flowing.
I guess I never did explain the flexable troops/goods system properly...
Think of what it takes to equip an infintaryman. A spear, armor, sheild, sword? First, would all infintary have the exact same armorment and equipment? What if you could make up "new" units by pieceing together what equipment you the unit to have? The player would have to ballence the cost of produceing this equipment (see point 2) with the benefit it brings. Second, what would it take to produce all this stuff? A logging camp would cut the wood, then a woodturner would have to make the wood into a spear before an you could equip an infentryman with it... Or any number of other examples of the number of industries and goods that would play a part in the player's economny.
This is interesting thinking, and obviously has greater semblance to reality. I think that equipment would be an excellent idea for the market system, as the greater the number of goods, the better. Furthermore, it'd allow far greater customizability of a given nation's army, rather than the current set-unit values. It would simply require a bit of time, were it implemented, as it is another large alteration, I'd think.