Re: Hey, I'm a card-carrying member of the "Over-thinkers Club," too, so hey.
So Moon is intellectually Loz + Yazoo. OK, then. >XD
I would say tha the "standard" FF-verse language is English, given that all the signs in Advent Children were only in English in Edge. In ShinRa-run Midgar, before the game, and in CC, signs were in English and in kanji (and everything was written in English, on papers and such, even in BC, even though they were speaking Japanese--which I'm writing off as "made by Japanese people so it's in Japanese"). Which to me, and this is speculation I'm using in what I write, indicates either a) a sizeable enough Wutai population in Midgar (because you don't put things on signs like that unless there is a need for it), and/or b) in the past, the area around Midgar was, in fact, held by the Wutai. To me, the fact that official numbers for the sections are in kanji, indicate a hold-over from being held, and ShinRa appropriating them as a way of keeping that feeling of authority that would have been left over even after the Wutai had been run out--it gave that feel of legitimacy (since the Wutai invaders from back then would have insisted on Wutai characters being used as they were in Wutai, but only for official things. This is also why Shinra has kanji for their name and use it in everything--that idea that the rulers use these), and once ShinRa was gone and people were rebuilding anew, they dropped that last bit of unnecessary past--no one used kanji to read anymore, so there was no point having them. By then, the use of characters was tied more to Shinra than to Wutai, and both were unnecessary for life now.
...Yeah, so, you just hit on something I'm thinking about a lot for a fic I'm working on. Um. Yes. ^^;;;
Like I said. I'm going with ta because, even though my brain wants to then switch to Chinese for a couple words, that seems like it's less of a headache, yo. And birds might have just the cloacca (spelling MISS! Six years in Japan will do that to you), but gender is there somewhere, but I don't suggest the way of sexing them that people use on birds and snakes--poking a stick up there and seeing how far it goes. Something tells me Moon might have a few...objections to that.