
Lore wise the M4X is intended to be a replacement for the ageing M3 Pattern Armour, but it is still in experimental testing.
Benefits: The reasons I want to suggest this is twofold.
Firstly it would be a more lore friendly change, since this armour actually exists in the lore whereas the B18 does not, heck the actual entry for this armour states "While the M4X is superior in all aspects to the M3, the armor is still undergoing field testing with several Marine combat units before being issued to the entire US Colonial Marine Corps.".
The second reason is that the M4X would look more unique in game, and be easier to identify to both Marines and Aliens, considering that this armour in game already has many qualities the M4X has (acid proof, pounce proof, more resistant to attacks and has better facehugger protection).
Also makes more sense that this armour would offer better protection from facehuggers due to the visor.
Implementation: A new sprite would have to be created.