I've a few suggestions for your excellent mod Plutarck. I'm not sure if these have been mentioned before because I haven't read the whole topic (19 pages!).
One thing that really annoyed me about Civ3 is the lack of units. Most ages would only have three ground units- one attacker, one defender and a bombarding unit. In the later ages, it would be just restricted to tanks and mechanised infantry, which is hardly realistic in warfare. You've done a great job in adding attacking and defending infantry along with vehicles. However, tanks and mechanised infantry are not very common, and the majority of battles are fought by infantry. You should give tanks a much higher attack rating and boost the shield cost too so that tanks are not the dominant unit but they are very important. This should be done with most of the later units (planes, Mech Infantry, Spec Ops, etc).
Bombarding units and cruise missiles should all have their bombard attack and range increased but so to their cost to make them more effective.
Musket Infantry should be upgraded to Shock Infantry and then to Modern Infantry. Machine Gunners should be a artillery unit with 1 range but a high rate of fire.
All ships should have their shield costs increased. Battleships, Aegis Cruisers, etc should have thier bombard range increased.
Archers and Crossbowmen should be able to bombard.
Mech Infantry should be able to carry units.
You should be able to make a army for every city, but the cost should be very very high.
What about a attack helicopter?
Horses should increase shields not food.
I'll give you a chance to reply to these suggestions first before I give you some more

. Once again, good work on this mod. You've made a great game even better.