I think the M240L should be the main gpmg used by the us army and the M240B should be used as a secondary mg kit for the us army. The M240G can be a secondary MG kit for the marines while the m240B will be the primary mg kit for the faction. This setup fits the timeline that squad takes place in.
#M240L and M240B MG
vernal vigil
mystic vale
It would have literally zero impact on gameplay
M240L is literally just a lighter version of the 240B
And the 240G is literally just a modular variant so you don’t need multiple different varients depending on wether it’s vehicle mounted or carried by infantry