This worked great, seems to have fixed most of the issues I had when just building the packages.config directly and does seem to correctly invoke mgcb. All I had to do was recreate the config/dotnet-tools.json manually as visual studio would not accept it when being downloaded from elsewhere.
Do note that if you run the game in debug mode it will frequently crash when trying to load a save file, probably a race condition for initializing render targets that doesn't seem to happen in release builds.