If your goal was only to make a good launcher, it would be easy. If your goal is a lot of DRM shenanigans as if we were still in 1998, it’s really hard.
I can understand wanting mods, but at the same time, it’s not like you can open your iPhone without damaging it in the process. I guess I want to say that I can get why people would want to add stuff to their thing, but I don’t see why someone would expect Valve to have accounted for that.