I don't think Model editing is possible without actually learning how to convert to the Dissidia GMO format perfectly, however, I have gotten texture modifying to work before.
Don't know what I can tell you without getting in trouble, but the Dissidia 'GMO' model format contains the 'GIM' Texture format, which is the standard PSP format. What I also know is, there are two different GIM converters you can find on the internet. They are both the same program, but they are different versions. The newer one will allow you to convert from a workable format to a special type of GIM I dubbed "SGIM" for my own reference, and the older version of the program, which is slightly more hard to find, will convert from "SGIM" to a 'GIM' format you can then hex-edit into a GMO file with the right tools. of course, textures will need to be kept the same filesize or smaller to keep the model size the same.
...I think the program is called GIMCONV.
I experimented with Cloud once, trying to wrap Crisis Core textures around his Dissidia model. I warn you, if you try this, don't try to mod any animated textures, it doesn't work like you'd think it would D: (as you can see in the screenshots)
http://i182.photobucket.com/albums/x74/beefpwnage/CloudView.jpghttp://i182.photobucket.com/albums/x74/beefpwnage/Fight1.jpgTL;DR:If your hearts are set on creating entirely new GMOs readable by the game itself, I suggest you google Rich Whitehouse's website, check out the GMO format specs, and try to write some code to convert .dae format models you might have into readable GMOs. I can see it being somewhat possible, but you may have to make sure data needed by the game such as model name and bone names as well as collision data etc. are all correct.
Anyway, I'd be hugely interested in the taking on of a feat like this, and seeing as (at least the 3D side of) the GMO format is perfectly compatible with Dissidia Duodecim, it would definately be a worthwhile goal to work at!
