mods that cannot initiate network connections or the local filesystem are not that much of a concern, but running an arbitrary C# program as your local user to me is a significantly different use-case, I think the steam workshop should integrate a checksum approval process where a user can decide for each individual update if they want to install or not.

I personally have bought skylines and find it great, but I am really wary about downloading mods for it as things stand now unfortunately.