Reverse Porting FFH feature back to Civ 4

So I really like how FFH handles great generals.
The gradual accumulation of experience over time was an amazingly good idea much better then the original way generals were implemented.

I want to import this type of experienece gain back into generic CIV 4.

Can anyone direct me to the code that controls this feature. I should be able to (with time) take it from there.