The Flex MAG 58 MG on armoured veh's (Aust), has the coax type gas reg, which is very much user friendly. it would be nice if this was incorperated on all guns, but this would be costly.
There already is a Picatinny rail on the feed cover, and one can adapt the C2 sight to the reciever.
The US manufacured M240B, has a barrel shroud and a different type flash suppressor.
However, the US bipod differes from the standard FN MG, and in my opinion is inferior.
I find all bipods weak and too light for the gun, Australia has incorperated a 'bipod heavy duty', but this is now being removed from the system through attrition. We replace bipods often.
My 2 cents.
Pics- standard Aust Mag 58, US M240B, and the Aust 'heavy duty' MAG 58