Side note:

If anyone is interested i have a quick and dirty fbx to mdl converter POC, written with FBX SDK 2014 and mdl7sdk from the download page.

It only convertes meshes/textures/uvs/groups though, no bones(hence no rigging) or frames/animation(since there is no rigging).

p.s. by quick and dirty i mean: Mashed together in couple of hours for fun a couple of months ago and i myself probably would not be able to look at the ugly creature that it is right now.

Also if anyone wants to go down that path, mdl7sdk docs consists of a sample code file, and fbx sdk always explains exporting to FBX, the exact opposite of what you are doing, so you basically need to do things in reverse from the docs.