As requested by HeelX in this thread this tool splits a mdl into its groups and save them as individual .mdls.

Download
You need to copy the wmpio.dll from your gstudio directory to the same directory where you saved the splitmdls.exe.

Usage:
splitMdls.exe fileName [options]
options:
--ext EXT: save skins as external textures with file extension EXT (3 digits)
--offsetmesh: creates an additional mesh with vertexes at the group positions
--nm: adds normalmaps as external textures with ('SKINNAME'_nm.'EXT')
--all: every group model has the same skins
--disableMat: removes all material definitions from the skins
--wmp: creates a wmp consisting of the group models
--help: displays this

If you use it, don't forget to thank HeelX who sponsored the development.
If you have any problems or some suggestions just name it.