I've added this to my TODO list some time ago
https://trello.com/c/ne2pb3f8/135-support-ue2-skinningstreamThis issue is common for Echo of Soul game, and appears for a few community meshes/mods for UT2004. I have no idea what tool was used by community to strip editor information from meshes (which is used by UModel) - but they did something what was not possible with tools available to everyone. Probably that was done exactly to protect from mesh extraction, or to save memory when running the game.
This task has very low priority, because it is for very old technology, with low quality of content (compared to games made today). Also it is very hard to implement, it requires a lot of reverse engineering. So the only possibility to work on it if I'll become jobless one day, for a long period of time. Of course someone else could work on it as the source code of UModel is fully available - however I didn't get any significant contributions since the source code release.