I think it is very hard to do a body with good proportions, still trying to find a good proportion for my base model...
One thing that helped was try export my model to Unreal 3.
This is how it was my model, using some screenshots from FF-AC to use as reference:
This is after using more or less Unreal Tournament 3 base female model proportions.
I guess it isn't set with the bumpmaps i made.
The wireframe shot below is from my latest update i did to my base model, acutally i picked a FBIK sample that comes with maya, all i needed was the joints with the right names for FBIK support. Then i posed it more or less at the spots, actually made the legs a little shorter.
In case you want to see better tifa face, using maya hair, but the eyes are still an older version.
The new eyes i made, still not very good, only used at belldandy and valkgirl:
in case you are wondering, it is the very same face i did for Tifa.
I have yet to update Tifa with all the latest pieces.