The big thing with any autococker is the barrel fit. So it would be worth spending some bucks on a barrel kit. After that the cheapest Sport body you can find is all you need for a slick pumper. And I like the idea of the basic CO2 feed. The vertical gas through grip would act like a sort of expansion chamber . Or better yet get a smaller actual expansion chamber and you're all good to go.
I had a "Paintball God" moment once.
Like Al Bundy's Polk High football moment I live on
for the slim chance of repeating that one time
miracle in some small way.........