I agree that Finn’s character is inconsistently portrayed. At some times, he’s the guy who just wants to do good and get along with everyone, then he’s a self-interested coward who kills when it’s convenient. Fear of the First Order drives him to cowardly running away, but there’s also an underlying decency. I think it’s the conflict between these two drives that make him a compelling character to me, and also why it’s almost a universally agreed-upon edit to remove him mowing down Stormtroopers when escaping the Star Destroyer. Finn doesn’t strike me as being angry with the First Order to the point of murdering his fellow troopers. The line you bring up, ‘Because it’s the right thing to do - I need a pilot’ is good because both things, I believe, are true for Finn. When you humanize a single Stormtrooper, surely this should mean that the story treats them as more than endlessly disposable soldiers.

It all comes back to his first scene in the village. Finn wasn’t acting out of self-interest when he failed to kill the villagers, since he was in no danger. Instead, he put himself in danger by not following orders, an inherently selfless act which exposes his ultimate conflict. So if your thesis is that Finn begins the movie as entirely self-interested, his first scene doesn’t bear this out. A selfish person would have killed those villagers to protect their cover and run at the first opportunity. This tells me that Finn is definitely not motivated purely by self-preservation, but by refusing to kill except in self-defense. These are very different things.

I’m considering how to show this through edits, and I think I can do quite a bit to make Finn more hesitant about killing, beyond the hangar escape. For example, make him fire to destroy the TIE fighters in the desert only after the Falcon has taken some serious hits, and remove his violent murder by lightsaber at Maz’s castle. Every time he kills a fellow trooper, it should weigh on him in some way. I feel like this is the only way Finn makes sense.