I dabbled in texture editing a bit ages ago, but since I couldn't figure out to literally build models, I gave up on it.
From what I recall of the process I used, the old FFXI Model Viewer had a button on it called .DAT to MQO or something. When you clicked that on a desired item, it broke the specific DAT into 4 pieces. From there, I think one was a very small file for the texture (and it's kind of maddening to believe what you see stretches out into what we get) while the others contained the wireframe data and who knows what else. I think when applying texture changes, I used a program called gc3 (Graphics Converter 3, that might've been found on the same site as the old MV) while something like Metasequoia could manipulate the wireframes to some degree (Like if the MNK pants had enough anchor points, Kohan could actually get them a more muscular look, but you couldn't actually create new points since the texture files wouldn't know how to wrap around them).
I'm sure the process has improved since then, or at least people have a FAQ up somewhere, but for someone just looking to dick around thinking they can create quality stuff, I'm gonna say not likely unless they're actually experienced with CG art programs. Otherwise you get things like Kohan mentioned with washed out colors, or people with all sorts of clipping issues, no or poor skeleton weighting (think male elvaan casting flaps), and so on. :/
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