Source code for various SFM plugins I made:
Visual Studio 2022 or newer is required with MSVC build tools downloaded.
Open the sfm_plugins.sln and build.
I recommend changing the Output directories to your SFM's addons folder in usermod.
SFM, like most other Source games, has support for loading server plugins
It turn out that after patching where the engine searches these, it's possible to load them from the workshop. See Plugin Loader script.
This allows for more sophisticated patches to be made on SFM than would be possible with Python alone.