The first thing that struck me when learning the basics of this game is this: the resources seem inexhaustible.
It would be interesting to see some kind of depletion mechanism along with prospecting technologies and activities, to cover the surrounding area. i.e. a player improves their chances by investing more in exploration and the related technologies.
This would require different commitment for each resource, because they are hidden to varying degrees [f, w, c, s, i, g]. Oh, and add in gold deposits to sensible places while reducing the current harvestable gold.
This is different from the existing sov buildings, because the existing buildings offer certainty of resource generation, whereas the above proposal is based on probability.
Sovereignty claims would make the process more secure and better-maintained, but I suggest that the farming/mining activities be run in parallel with the sov buildings, rather than be a mutually-exclusive activity on a sov square.
This would give players more reason to be territorial, and to use sovereignty as a territorial right to exploit the land. Where there are variables that create conflict and overlap, games become interesting!
Long-term, I expect this might create land pressure, and a sense of having burned out the land if over-mined. Having an active landscape might help renew these resources and shake things up a bit. An alternative might be to allow (expensive) regenerative magic every 6 months or so.
Edited by Albatross - 31 Aug 2011 at 10:17