My initial thoughts are, make it about both of them. For this to ultimately makes sense in the long run, he (APEX) obviously escapes into the wild at some point to be the subject of sightings. But then we reach the issue of one male does not make a species. A male and female could. So, if she’s thrown in as part of the team who helps create APEX, and Hatch is the antagonist, and he’s borderline insane about weaponizing this thing, then you could take that route. She could either develop feelings for Webb. She could empathize with what is happening to him and somewhat disagree with the experiment on moral grounds. Then, perhaps, Hatch sees this and does the same thing to her. Maybe they learn how to stabilize the compound by then and create a pair. That’s only one way to go with it and it’s your story. It just makes sense that in the end there needs to be a pair that can create offspring.