Thanks again guys!
Nice&clear presentation you posted there Styves! Maybe not perfect, but using a good old Lookup Texture / BRDF instead sounds a whole lot easier! Only little problem is that when using a Deferred pipeline like I do, you also have to store which BRDF to use, assuming that besides skin, we have would have a couple more profiles. You could put all possible BRDF LUT textures into a big texture, and use 1 gBuffer parameter as an index/offset.
For larger, not-so curvy surfaces, Pre-Integrated Shading won't do a whole lot, neither does it give us backlight. But for that I'd like to give the Frostbite approach a try. That probably means each vertex will get 2 extra attributes "Curvature" (For fake SSS) & "Thickness" (for backlight). Only thing that still won't work, is backlight coming out of a lightmap or probe... Oh well, let's just make & check this out first!
Well, I'm informed now, thanks again!