I was actually previously working on a Touhou mod myself. It was to be all inclusive, containing 10 civs based on the original Touhou Jojishi from Civ4 (the 10th being the Ten Desires civ) with leader traits generally based on what civs/leaders had in that mod.
The leaders were to be "balanced" by each one being very powerful, as per classic Gensokyo powerlevel warfare; Eirin would get mad science/growth/specialist bonuses, Koishi would get free courthouses/minimal resistance and would have an Rome/ICS playstyle, Cirno would have lower science and weaker unit strength but can mass units really fast and extremely cheap upkeep, Reimu would get majorly increased gold in cities and would have extremely powerful Customs Houses, etc.
Unique units and buildings were initially going to be 1 unique wonder/building that would be very powerful and 1 unique "Boss Unit" that would replace a typical unit - a Momiji that is a super-mobile Longswordsman or a Yukari that would essentially gap via Paratrooper mechanics, for example. Later on as I would do more research and learned how to use Lua or DLL modification better, I would shift back to individual civ techs and single boss units that would upgrade as you go through the ages just like the original mod.
I just kinda stopped working on it, largely because I'm not great with modding. Perhaps a bit too ambitious on my regard. I still work on it very very occasionally, though...
Then again, thanks to the sudden influx of Touhou mods, I'm kinda getting interested in trying to work on it again
The ambition! It's too much for me! Nah seriously, that's a pretty big goal for just 1 man. For now we're doing separate civs to add to the vanilla ones (try not to replace vanilla civs if you make one) and we are in no position to object you joining the mod crew . Still, if you want to work on a separate civ, post the character or group you are making a civ on (so no civs repeat themselves). If you want to keep working on that HUGE mod, be my guest, we'll help you with what we can.
Welcome btw