I did see one person do it and i thought about it but i did not like cutting a hole in it to have the air line come out of.
I have thought about modifying the mag so gas section is semi pertinently installed in the gun and the BB tube is the only thing that would come out so i can reload it. The air source would somehow attach to the mag through a completely internal gas tube leading to the but stock where i would have the RIG so i could change out the 12g's when needed.
But that idea requires alot of work and skills.
The ARES AW338 has a magazine system that is 2 parts 1 is the gas well the other is the BB shoot
Thats what gave me the idea about fully internal gas system because i would not need to take out the gas well only the BB Shoot.