Why are you getting hung up on this .xbx it means nothing but the platform these files are intended for and if you understand the data enough to do this the changes between platforms aren't going to make or break a project. The extension you need to be concerned with is the next extension over as THIS IS the particular file format.
The main issue is the skeletons aren't the same. In THPS3/4 they use an X pose where THUG1/2/THAW they use the T pose and the joints are all wrong.
Even IF there were a plugin to do such a thing in a modeling tool such as blender you're going to have a world of trouble getting it to work in game without tons of work.
Then there is the issue of exporting it into a THUG2 compatible format.
This post isn't designed to deter anyone away from this task, but instead inform you that the assumption that all the stars are going to align and you're going to be blessed with tools to do all the work for you without having to do 1)Write or modify your own tools to aide in the task and 2) Lots of work to get it to actually work is a pipedream at best.
.skin's are model format and typically used for skater skinnable objects.
.tex files are a collection of .img files.
i was aware that the .xbx extension isnt really that important in regards to actually opening the files and has to do with what system the game was intended to run on, what im confused about is how do i add that extension back onto something after i edit it. like, if i were to dig into a .tex file, change a texture around, and save it/run it thru a tool to convert it back into .tex, how do i put .xbx back onto it after that? is it as simple as changing the name back to it, will i be able to export directly over the original file and retain that extension, or is it more complicated than that?
i figured the skeletons between the two games would be a major issue, as THPS3 skaters werent designed with THUG mechanics in mind, in addition to changes between engines in the time between the two. id like to see them side by side just to know how drastic the difference is. though i disagree on the X pose from THPS3, i just opened up Wolverine in Blender and he is definitely in the T pose.
i didnt expect this sort of thing to be easy, im more interested in knowing if theres any real interest in this sort of thing other than from myself, whether or not anybodys tried toying with the models before, and if anybody else has any ideas relating to it. it would be stupid for me to expect to instantly find all of the answers to my questions like this if nobody else has even considered tackling these problems.