Re VFC. Usually the first release of a new one will have two versions, a plain package and then a DX version. So the Mk 16 got 2 inner barrels, and a case. The EGLM comes all singing dancing with 3 magwell groups.
Then later they'll just sell the plain version with one barrel, no case, and so on.
So if you do see a VFC model you like get the first round with the bells an whistles.
And last point, there is a GBBR Mk 16 in the pipe from these guys, various pictures are up on this webiste. For the folks trying to puzzle out internals they now have a listing of the M4 spare parts on their website.
Airsoft, where nothing is hurt but feelings.