Things I've noticed that are easy to miss:
Vents: On either side of the upper torso in conjunction with those already existing on the front of the torso (much like the ones the GM Quel has)
Shoulders: Resemble that of a GM Custom, almost combined designs of Mk II and GM Custom Shoulders
Skirt Armor: Its just not the same, again, more like GM Quel
Rear Legs: Thrusters that weren't there before
Backpack: GP-04G Backpack design
Optional Armaments: Shield and Rifle are completely different.
Check these analysis for yourself>
Mk-00Mk-II