Let's take a look.
Equipment:
L119 Bolt-Action Sniper Rifle(Suppressor)(Bipod)(Variable-Zoom Scope)
9mm Pistols (2)
P90 Sub Machine Gun(Suppressor)(Variable-Zoom scope)
Climbing Kit(Iridium Claws & Boots)
C4 Plastic Explosives (6)
Iridium Katanas (2)
Standard Combat Uniform(Black)(Hooded w/ half-mask)
Mk.1 AR HUD Glasses
There's your equipment. GM's fiat, most recent update. Now here's your equipment with approximate uses and ranges, based on the description and likely GM ideas about it.
Equipment:
L119 Bolt-Action Sniper Rifle(Suppressor)(Bipod)(Variable-Zoom Scope) Long to medium range, stealthy, high accuracy; best for heavily armored or high-value enemy infantry.
9mm Pistols (2) Close range, hold out weapon, moderate accuracy; rarely best option, save for light mission load requirements, in emergencies, and in case captured and/or searched
P90 Sub Machine Gun(Suppressor)(Variable-Zoom scope) Medium to close range, stealthy, moderate accuracy, high rate of fire; best for lightly armored enemy infantry and in emergencies.
Climbing Kit(Iridium Claws & Boots) Not a weapon.
C4 Plastic Explosives (6) Multi-use; primarily used for stationary hard targets, and traps
Iridium Katanas (2) Melee, stealthy, extremely sharp and hard, very fast; best for melee assassinations and CQB.
Standard Combat Uniform(Black)(Hooded w/ half-mask) Unknown as to armor capability, moderately stealthy.
Mk.1 AR HUD Glasses Not a weapon.
You have something for most everything. Which isn't a bad thing. Really, the bad thing is that you don't seem to have a consistent idea for your character.
For example. You said this:
And I'm expecting him to never become as good in any one role as any of you will.
I didn't ignore what you said, I understand it perfectly but I do not want to edit a character that I already completed, in future characters I will take into account what you've said. All I could remove is medium range but he doesn't really have medium range weapons in any case. Short range and Long range are essential for him.
which contrasts with this:
Ranges and such can be done alone at a push and as long as you stay outside of extreme distances.
As for watching your back, thats a large part of the reason he hates being in groups.
He's always worked alone so in his entire career if he's had somebody behind him it's meant an enemy has found him. Operating in a group is going to be difficult for him and having a partner if either of our last 2 members is even capable of taking that role would be next to impossible for him until he's been around you all long enough to trust you.
Finding his target in this situation is not a problem since his primary job will just be supporting all of you, no specific target to kill unless the general assigns him one beyond order of prioirty in battle which in his case is basically just enemy snipers die first then officers then everyone else.
Other then special circumstances like artillery spotters or chooper pilots.
Focus is just a matter of discipline a single man can maintain it for days but it does have side effects that vary depending on the individual person.
Harvey is the total opposite, all of you are more skilled Harveys limited skills are just more refined within that limited area making him superior in one role and inferior in every other. I designed him with the specific purpose of being good in only one specific role.
As well as saying things like this:
Simple. if the enemy ambushes all of you which of us is best suited to turning an ambush for example?
3 people who will make so much noise the moment they move in that the enemy will know you've arrived? Or the guy who can drop a squad 1 by 1 in complete silence to open an escape route and plant explosives to distract the enemy when you move.
Of our group my characters skill set is by far the best suited to being the wild card of the group because I have special forces level training in blades, pistols and scoped weaponry and above special forces level stealth and stalking training plus stealth armor as well as demo training. My skill set is the most varied which allows me the most flexibility when reacting to situations.
Look at you 3.
A medic with heavy weapons, good for supporting fire and keeping us fit but limited other uses.
A combat engineer, heavily armed and armored but this also makes him slower and noisy.
Support engineer, very slow, heavily armored, medium armaments and limited support capability.
Each of you 3 is built more as a supporting aspect or as a piece to build a full team, where as I'm built both for support and solo operations. None of you have the skill set to operate alone like I do.
Then mine, medium armed with short, mid and long range capability including AP, HE and HP munitions as well as explosives, lightly armored but with stealth system. Arguably one of the nations best when it comes to stealth and stalking as well as elite level combat training and explosive training.
Of us 4 which one of us will be best suited to moving alone and reacting to enemy threats quickly without causing a bigger commotion?
I can take out infantry, aircraft and vehicles alike completely alone and without exposing the group in the process.
So which of us 4 is best suited to being the wild card of the group and staying unknown to the enemy until they need to move in? As I see is the most important trait for the wild card to have is the ability to remain undetected.
But then you say this:
... No he's not. A Mary Sue is somebody who's perfect at everything not in one specific and well defined skill set.
He has a very specific and defined skill set in which he is very skilled, take him outside of that skill set and he has 0 training and 0 experience and will likely die in 30 seconds flat.
He's good at stealth and covert killing. He has experience in sabotage. Thats it.
Put him into a direct battle or take away his ability to sneak and he's worse then a raw recruit. Which makes perfect sense because his entire career is based around avoiding detection and removing specific targets.
Now, being an uber-specialist is fine. Being a jack of all trades is fine. But you can't uber-specialize in being a jack-of-all-trades. Look at my character, for example(mostly since I know mine basically from memory). I am good at all ranges. I can affect all targets(except for some types of aircraft, but who's going to attack us with fucking jet fighters?). However, I am best at certain situations. I specialize in a specific thing that, with creativity and ability, can perform in most roles fine, even if it isn't great in every situation. I have missiles(on the UAVs), mag-charge grenades, and C4 for destroying helicopters, vehicles, and buildings all. Machine guns(again on drones), an assault rifle, two pistols and frag grenades allow to me to suppress enemy infantry or mow them down, participate in fire-fights, have a hold-out weapon, and drive foes from cover or clear a room. Two knives(I have two pistols and two knives because I want a backup knife, a backup pistol, and they're good for different situations) even allows me to fight in CQB. EMP grenades, smoke grenades, S15 Wireless Etc., A52 EC Suit, and an engineering kit gives me out-of-combat utility. Long range is covered by drones, medium range by rifle, and close range by pistols and knife.
Here's the key difference; my character isn't particularly great, or even good, at most of this. She excels in two things; Drones, and Explosives, both of which have significant, if not immediately obvious, drawbacks. When using drones, she's pretty vulnerable, comparatively. Her attention is on the drone, she can't really change positions, etc. Explosives has one in that it's not directly combat-focused, when we're in a game centered around such. She's also not overly-'powerful' in terms of her history, appearance, or personality. She's a relatively normal person(normal for someone who's one of the country's remaining best, since we all ought to be).