Regarding shader data in Shaders_Win32.precomp and porting TSM shaders

We've been talking about this on ModTheSims for longer, particularly here, here and here. The Sims Medieval runs on the same engine as TS3, and most data for it can be ported between games. Particularly TSM's subsurf scattering has come up as a highly interesting shader we'd like to see ported, but there's little knowledge on the workings of the precomp file. TS3 and TS4 both use this file, and SimGuruModSquad talks about it on the TS4 side of things here.

So uh.....how to read - and modify - the precomp and what's the potential of it? Someone made a Reshade-like mod for TS2 that integrates extra postprocessing into the game's executable without having extra software run on top of it. If there's any potential at all for that here, it's worth exploring.