A lot of the conceptual designs were done by Amano, then developed by Nomura. Even in FFVII, there's Amano art for all the characters - including a blonde Tifa.

The re-released version of FFVI is quite interesting, because its FMV sequences use characters based quite directly off Amano's artwork.Celes and Terra are practically indistinguishable, except that Terra is even skinnier. Their costumes are definitely creative, but wouldn't work too well in battle. Same goes for Yuna's and Lulu's garments in X.

Anyway... the designer isn't wholly responsible for how the character looks and acts in the finished product. The cast of FFVIII and X all have totally immaculate hair, skin and clothing - even after they've just been through a hellish battle and days of living rough. Those kinds of details have more to do with presentation than by design - how the directors and animators choose to make the characters look. For every character there are probably dozens of other concepts that were rejected.

Personally, I love Amano's artwork for FFIX. The game would've been considerably better of the characters and architecture had remained more true to his designs, in my opinion. Steiner actually looked like he meant business, and the cities had a look of ancient grandeur. However, it'd be impossible to turn his designs directly into in-game imagery - Garnet and Zidane are devoid of skin colouring; Freya's features are practically unidentifiable, and Eiko doesn't actually look human. Still great designs with a lot of imagination, though.

I guess my main point was just that the appearance of a character in a finished game isn't totally the responsibility of the designer. There's a small army of folks working on any given project, and the artist probably doesn't have too much direct control over what their design finally becomes.