So even though Pacific Rim is a new fandom, you're already getting some common fanon and common situations that get written about over and over again. These are two of those situations, but these fics take a different (often darker, sadder route).
A Touch of Blue How Mako comes to die her hair. Bonus points for involving Tamsin Sevier, Stacker Pentecosts copilot, who dies just before the movie's timeline. She appears in the prequel graphic novel. I would love more fic with her. This fic is heartbreaking in all the best ways.
Late Night Comedy Show Souldbonding/the drift is what makes the fandom. I see why Chuck/Raleigh and the science bros are such popular ships because of the relationship dynamics. I know that Raleigh/Mako is a popular one too, but because canon centers them as a sweet/warm/fuzzy semi-platonic pairing, we see those kinds of traits repeated in fic (they're so tragic! but they found each other!). Don't get me wrong, there is a place for that, but sometimes I want a the drift not to be the end-all, or I want the drift to be approached with a little more nuance. So this fic does that and the drift starts the same and ends up looking very different. And disturbing.