Can a GA headset be used for listening to normal audio or with a cell phone?
I actually know a guy that does this. He bought a nice noise canceling headset but then stopped flying and now he uses it on long flights and quite enjoys it. For what its worth noise canceling headphones have come down in price over the years and you may simply be able to sell the headset and buy a less bulky set of headphones for the money you make. But if you dont want to go through the hassle then there is nothing stopping you from using aside from having a boom mic dangling off it. 

For what its worth a lot of noise canceling headphones now have mic inputs as well so you can answer calls from them as well.