Ok everyone! Good news!

I dived into D3D and it's really not all that hard

I have found a way to do this and maybe I can release a rough plugin as soon as tomorow. A touched up version should be done at the end of the next weekend. I have exams next week, so I can't work on this during the week..

What I've got now:
A plugin that can copy the normal UV Map to the second UV map. I can test this with two small shaders that use either TEXCOORD0 or TEXCOORD1 for texture lookup. When I launch my app, the warlock looks normal with the TEXCOORD0 shader, and messed up with the TEXCOORD1 shader. If I call my plugin function, the TEXCOORD1 shader will look correct (because the TEXCOORD0 was copied there).

So the only thing left to do is write a function that can read in the UV coord, instead of copying the first UV.. I hope the skin points exported by 'export skin mapping' in MED are in the right order, or I will have to come up with something clever..

@Ventilator: the vertex format used by 3DGS already has 3(!) texture coords per vertex, thus no need to duplicate vertices.

EDIT: could someone (frank?) send me a model with 2 UV maps and a shadow map? You could send one .mdl with a normal diffuse texture and the normal skin mapping, and another one with the shadowmap and different UV mapping. My email is taco dot cohen at gmail dot com.