Sounds like a wonderful idea to me. If it has a reasonable price, I'd definitely buy it! I could use my collection of V3 textures on V4, some of which are never to be converted by their authors. (I understand their creativity brings them to think about something new than remaking old works... but each character is unique and I want them all!)
BTW, if you could write a tutorial about remapping textures, I'd be VERY grateful, as I have the same problem with Miki 1 and 2: the differences in mapping are really small, but nonetheless, textures for Miki1 won't work on 2nd version, and I just want to use Nubya on Miki!!!