Here's a very basic marine. I used the template from GURPS Space. The character is built on 150 points, though only 130 have been allocated--that should give plenty of room for some non-combat customization (though I'm sure players would likely boost the relevant gun scores, and maybe add some different specializations). I won't worry about MOS's right now, and the main point of differentiation between characters will be weapon load out. So I'll kit out ten of this guy, and play test combats for each team (Attack and Weapons teams from the Bug Hunt Infantry Squad post).
Marine (150 points)
Attributes
ST 11 [10]
DX 13 [60]
IQ 11 [20]
HT 11 [10]
Secondary Characteristics
Dmg 1d-1/1d+1; BL 24 lbs; HP 11 [0]; Will 11 [0]; Per 11 [0]; FP 11 [0]; Basic Speed 6 [0]; Basic Move 6 [0]
Advantages
Combat Reflexes [15]
Rank 2 [10]
Disadvantages
Duty (to the Corps, 15 or less) [-15]
Code of Honor (soldier’s) [-10]
Overconfidence [-5]
Sense of Duty (Comrades) [-5]
Skills
Camouflage IQ+2 [4]-13
Computer Operation IQ [1]-11
Driving DX [2]-13
Electronics Operation IQ [2]-11
Explosives IQ [2]-11
First Aid IQ [1]-11
Forward Observer IQ [2]-11
Guns DX+2 [4]-15
Knife DX [1]-13
Gunner DX+2 [4]-15
Hiking HT+1 [4]-12
Navigation (land) IQ [2]-11
Scrounging Per [1]-11
Soldier IQ+2 [8]-13
Survival Per [2]-11
20 more points in skills or advantages
I should probably add something here.