I don't know if this idea has been brought up before, but I guess it wouldn't be too hard to create great military people, so they would be able to discover a new military-related technology etc.?

Or maybe, they could create a fat stack of units or give a free promotion/xp to every unit in the city they were in.

Someone already did a great General mod that does what you want. Search the forums for it.

Roger Bacon

Snaif made a great general mod that can be found under the Completed Modpacks forum. I have also merged his mod into my Composite Mod with about 11 other mods :P