(1) The MK20 (F2000) doesn't need the vertical grip on the monolith arms forend.. it somewhat defeats the purpose of having the forend installed in the first place. This would be a character modelling change for hand positioning.
(2) The polymer shrouds which surround the optic that are used on the military versions of the F2000 should be optional, and include the BUIS on top of the shroud (like in real life). The sights under the shroud should have either the 1.5x optical sight (black reticle) or a red dot (the C-More railway sight works in real life).
(3) The grenade launcher should be specific to the platform (as the F2000 has its own specific GL attachment in real life).
(4) If a grenade launcher is attached, the polymer range-finding shroud should be optional (and look different from the original shroud). This way, you could do away with the side-mounted red dot precise firing and have the precise launching capabilities integrated into the sight/shroud.