*edit. I should note a good modding api and/or editor is great for any game.
I started programming though making mods for battle for middle earth 2.
However, we must make sure to keep in mind the ways in which capitalists will exploit the goodwill of developers and free software wherever it may be.
Absolutely, modding is fantastic. And in some ways; It gives a unique avenue for artistic expression. A platform for 3d and textures art, memes, machinemas, and so on.