An update to militaristic city states?

I love militaristic city states, but I think as is they're a little too limited. I wanted to change them so that, in addition to gifting land units, they could gift naval, and even maybe air units too. However, I was looking through the files, and I can't seem to find the part of the code that says what type of units they gift in the first place. Is such a project even feasible, and if so, where would I find the file that would allow it?

CvGame.cpp, specifically CvGame::GetCsGiftSpawnUnitType()

Thanks so much. I'll try and mess with that tomorrow, then.