From your description I think you are better off not compiling the SDK in to your application anyway, I think when people over abstract their code too much it ends up bloated and often the team behind it are no longer capable of understanding what they system does anymore.
I have not looked at the Rift SDK - their site appeared to need a login and the effort involved in that exceeded my willingness to look but by what you say it sounds like they are using an MVC architecture - which is actually quite a nice way to work for modular and re-usable systems, but not very LFS'y.
It sounds like they envision the Occulus SDK will somehow form the foundation of a gaming project. If they believe that then they have lost sight of what their project is (cheesy pun intended) and/or have never actually written a game themselves.
This doesn't help however, but I think Ben might. Compiling a .dll with a few exposed functions is easy for any of us but I think he's a Visual Studio user with lots of experience in related areas and I'm pretty sure he's down with MVC architecture too, so he can probably knock you up what you need pretty easily. Visual Studio and me don't see eye to eye (cheesy pun intended) so I would probably struggle myself.
EDIT: Regarding your earlier question about differences between DX9 and DX11. The only real substantive feature difference that I can see in DX11 is Tessellation, it's a bells and whistles thing you can throw on top if present and the rest is just DX9. I'm using a DX11 engine myself but it drops to DX9 seamlessly, although I haven't actually played with the tessellation yet (I mostly code DX stuff on a Win7 machine). There's also some shader enhancements, the ability to run shaders on streaming video and something to do with shadows that I don't understand. It should be okay to migrate LFS to DX11 and use tessellation, but still run as DX9 on older OS' without it. Just be careful to test under DX9 when you start writing shaders.
EDIT 2: Oh here's a reason for DX11 in LFS. Rendering wheels with PN-Triangles would eliminate the polygonal artifact and give us properly round wheels so they no longer look like Captain Caveman drew them but under DX9 they would look as they do now, as tessellation is simply off.