Centainly the resource system could use an overhaul.
Gold is in real life not a resource. It isn't used in buildings, armory of suits. Iron is. Therefore iron is really a must.
I think four resources are really necesary. Wood, Food, Stone and Iron. Wisdom (or Knowledge) as a fifth, something like favor in AoM, not really a resource, but necesary.
Buildings should of course be made of stone (depends a little on culture and age, may some wood too). But for example a stone house in Imperial Age build for 25 wood isn't realistic. Stone should be used more in case of building structures. Maybe a transition. In the early ages it costs wood and later on stone.
Wood, is used to a degree in buildings, for archers and cannons etc.
Food, obvious, for all living things.
Iron, for more advanced units, with armour and all that. Also tanks and planes (but they're not gonna be in AOE3 I think). Phalanx's, armoured Elephants, knights, units like that.
I think gold should be degraded to a lesser resource of even removed in favor of wisdom. Wisdom (or knowledge) would be used for going to the next age, upgrades, things like that. I would be gathered by villagers or special units at a certain building, a little like is done in RoN.
IRL, I don't think there's place for gold. Trading could just be done with real resources, so one could give trading carts/boats a setting which resource it should trade, or just automatically get a resource of which there's not much. Of course silver isn't a realictic resource either.
[This message has been edited by Breepee (edited 12-15-2004 @ 04:23 AM).]