Conflicted!?
Chieftain
I think that civ 4 should offer you the opportunity to create your own units based on the current technology that you have.
For example, lets say that I have the technology for gun infantry(repeating fire). You could choose their Weapon, its statistics within its category on a scale of 5, such as an smg with 5 rate of fire, 2 damage, and 3 range. Also, you would be able to choose if/ and what kind of explosives or inherent anti-vehicle weapons they would have, plus maybe the percentage of the units armed in whichever fashion. The stats and weapon type and amount of explosives would affect the price/ production time of the unit, as well as its effectiveness against tanks.
For example, lets say that I have the technology for gun infantry(repeating fire). You could choose their Weapon, its statistics within its category on a scale of 5, such as an smg with 5 rate of fire, 2 damage, and 3 range. Also, you would be able to choose if/ and what kind of explosives or inherent anti-vehicle weapons they would have, plus maybe the percentage of the units armed in whichever fashion. The stats and weapon type and amount of explosives would affect the price/ production time of the unit, as well as its effectiveness against tanks.