I would like to see Civ4 have a random generator (+/- 20%) for every unit for every nation. This would allow that some civilizations produced better units of given types than other nations. As I mentioned in another thread, Japan and Italy had terrible tanks. Germany started with weak tanks and eventually made the best tanks. Russia also had really good tanks. Taking and Italian tank up against a T-34 was suicide!
Civ4 needs to allow a variable to units (one time set) that gives a +/- of 20%. Then if a player did not like his random draw (for instance -20%), he could re-research the tech to get those units to be better (or maybe allow the maximum--I'm not sure which, it would need to be playtested).
Thus, if France gets sucky tanks, they could choose to re-research armored combat (or whatever the tech was that gave those tanks). The advisor would say something like, "Sire, we already know that technology. Are you sure you want us to continue?" The options would be A: Oh, well then, nevermind. B: Tell those idiots that they can do better than that!
One of the caveats of doing this is that all combat values would need to be multiplied by 10 (assuming that you could also get +/- 10%) since the units would need to display the correct values. I, for one, would have no problem with warriors having a 10 attack and modern armor having 240. I can easily discern the ratios.