So I'm not sure that a piston gun has any distinct advantage here.
The big advantage with the piston system is the fixed expansion chamber/piston dimensions that remain irrespective of barrel lengths.
So you can swap out barrel lengths/uppers without needing to "tune" the gun to run with different gas pressure inputs. It is always the same, assuming you keep the required inlet pressure coming into the piston from the barrel. (You "should" be able to run a 20" upper and a 10.5" upper on the same lower without having to fiddle with the buffer.)
There is also the improved "over the beach" performance. But since most civilians aren't going to be swimming into an objective and popping up out of the water and "going hot" without having time to let the water out of the gas system it is kind of a moot point.
The biggest advantage I could see in fullauto is that it would require less lube to be added during a high volume shooting string since the piston won't be blowing lube out.
In my experience, when it comes to shooting suppressed, I can't visually see a difference between the amount of crud the gets blown back into the action due to the suppressor between a piston and a DI gun. Both absolutely cover the inside of the gun/cartridge stack with soot.
If you need any help wringing out any of those full auto guns, let me know, I would sacrifice some of by valuable time helping you turn cartridges into noise.