They've allowed Demo content to be converted before. rFactor has Blackwood RallyX. The devs are pretty nice that way.
Although that video does show that the lighting/textures in LFS is the true reason it looks kinda blah, as most NKP tracks have some more dynamic look to it, whereas the conversion to NKP kept the same lighting as the LFS version
Track mods aren't allowed and it's basically IMPOSSIBLE to make a track from scratch for LFS because the devs are magicians, and if there was a different track for LFS it wouldn't have the same quality as the ones we have already.