The FF1 they made for WonderSwan (And the PS1 port coming out) has been "up-ported" to C. Actually, all the re-releases have. (FF 1-2, 4-6, Chono trigger) This is because, unlike other companies, Square does not want thier software to suffer from bitrot. The up-porting will keep it portible for years to come.
3 is missing as the WonderSwan market tanked before they could complete thier backporting efforts.
Wonderswan.
On a slightly related note, the WS was supposed to come to the US. The problem was that Ban-Dai's US Partner, Mattel, wanted to market the WS as toy for smaller children, and not handheld to go up against the GBA. Sad really.
Anyway, don't knock the FF1 code, it's pretty complex. The world map bank (bank01, if I remeber correctly) has the RLE decompressor at the tail end of the bank. There is only about 20 bytes of clearence between the end of the map and the the start of the decompressior. It's a tight squeeze.
I'll clean up some of the code and docs tonight and post the thing here. I'm here all week for questions. I'll point you to the tools you are going to need too.