I resent or resemble that remark
Well, IMHO, twistlock barrels and the associated bodies are antiquated and should be recycled. So, not have the barrel lock retention pin there is a good thing. But its rather easy to put back. It is not a "press fit" or anything. Just literally, knock it back in. If for whatever reason you like standard, or powerfeeds with elbows, a cocker to mag adapter is paramount. With paint being anywhere from .665 through .690, using an insert barrel where you can dial in the bore size, does not lend itself to twistlocks (unless you have a twistlock freak back), as most of those barrels where in the big ball era where you can literally get away with a .688 all day.
Mags with classic valves can be run on Co2 because it is "blah, blah, blah". If you are talking about Emag/ReTro/Xvalves then HPA only. You have been in paintball enough to know the benefits of HPA in a gun, just as likewise with proper precautions, you get anything else to run on co2. With that, as long as you make sure that no liquid gets into the valve (remote lines is the best, with or without an expansion chamber or even a Palmer Stab inbetween the valve and the tank), you'll be fine as kind.
The key with mags is, keep the pressure above 650psi. So no SLP tanks.