are your asking if we would want a type 95 blowback design not gas.
http://sinodefence.com/army/small_arms/type95rifle.asp
machine gun in 7.62 belt feed.
I would say no I wouldent because the linked ammo is to close to your face.
bullpups are fine with 30rd magazines but when you throw belts into the mix
I think they would get hung up on stuff. that and with a feed tray so far back it would have to be highly reenforced in turn adds more pounds to the weapon
now if you had some idea of maybe holding it diffrent lets say on your shoulder and the feedtray and belt was behind your shoulder feeding out of a backpack or something that might work but then you would have the problem of going to the prone and the belt getting pinched.