To the “only one merc” thing
(I have written a really big analysis with references and explanations to this but since the webpage keeps refreshing when I hit the background panel, its lost and I wont rewrite those 500 words again sorry. Its lost. So here is the short version)
Jay Pinkterton has stated that there is only one every merc, one Soldier, one Demoman etc.. no clones.
I went through all comics and noticed that, of course, that we truly never see any merc “double”. But also never more than 5 from RED or BLU (with one excepting I will talk about later) The original team, the classic team and the current team shown in the catch-up comic has the same line up in a 4/5 split.
RED, as we know from the game is an attack line-up: RED Scout, RED Soldier, RED Pyro, RED Heavy and RED Sniper (all 3 Offense classes, 1 Defense and 1 Support)
BLU as we know from the game, has a defense line-up: BLU Demoman, BLU Engineer, BLU MEdic and BLU Spy. (2 Defense and 2 Support).
Throughout the story comics we get to know that the current team got fired, but also gets re-hired by Miss Pauling. Since then, every merc wears RED. We also know, that this team is hired to attack Gray Mann. And what did the latter do? Hired a defending team, the CTF, which are shown in BLU here. the current teams Medic gets also hired by Gray, but he still wears RED. This is the only confusing part for me, because he is hired to help defending, but it could also be meant as a hint that he is still loyal to the attacking/his own team (which he later joins!). The only mercenary from the current team who is not shown in RED is also the only one who is not re-hired by Miss Pauling in the story: The Engineer. He is hired by the Administrator, to build and fix here life-expanding machine, keeping her safe. He wears BLU and I can imagine why, because he hides together with the Administrator clearly defending and supporting her life. He is no way in any attacking position.
In the update comics we also see the mercenaries always splitted up in two teams, but we never see more than 5 people in one team (which also shows the team balance of 4/5 continually). Except from the point where the two Grey brothers die and MvM starts. Since then we only see the whole team, or rather both teams once, in the comic A Fate worse than chess. They are still 9 people, who just lost their jobs from both sides and they are also still evenly splitted into 4/5 groups! (RED(5): Soldier, Demoman, Engineer, Sniper and Spy; BLU(4): Scout, Pyro, Heavy and Medic). And also into clear defined defending/attacking sides. RED has 1 offense, 2 Defense and 2 Support which is clearly defensive, while BLU has 2 Offense, 1 Defense and 1 Support which is the Heavy, medic combo, clearly offensive. After that we see the whole team in a few more update comics, but also only shown in one colour: RED. They are re-hired at that point, fighting for the same side.
From this we can clearly understand what Pinkteron means. The mercenaries get hired by both sides alternating, probably the brothers trying to steal from each other by just paying more, so the mercenaries ge to switch sides as it comes. Blutarch hires the REDs Heavy by offering more money, then Redmond will hire the BLU Demoman in exchange by doing the same.
This also explains why they already know each other so much and work together so well in the story comic, because they all did fight alongside each other at least once.