It depends on what's going on with the game or mod. This is what a lot of people don't seem to understand. The game might be a decade old or more but it's still someone's intellectual property. The only hope you have is that the developer that made the game and the publisher go out of business and the game becomes abandonware. It's happened to a few games.
This channel is run by a guy who is making a remaster mod for the game The Simpsons Hit and Run. The game is abandonware so it will probably survive.
https://youtube.com/watch?v=7XGpU3qxMHk
I see people whine about mods getting hit with DMCA's as well. They go on and on about how unfair it is. But they never mention that the mod was using assets from another game or intellectual property.