Heh, that's pretty cool.
I considered modifying an electro pball gun to shoot airsoft. I bought a Mephisto electro to shoehorn into a CA 249. The plan was to hook up the bolt to cycle a faux bolt and shunt much of the gas out a port to make a nice loud noise. Ended up ditching the project. Too much engineering for a one off custom gun. I don't have the time for career guns anymore.
Want nearly free GBB gas?