I'm looking for a squad or small unit, tank, etc. shooter that has a sense of... idk, development? narrative?
I am not going to articulate this well, but a game that lets you take your squad, tank, whatever through endless missions and make them feel like your own. I'd say something like War Thunder or one of the many tank arena games fits the bill, but there's such a lack of permanence to your vehicles it becomes just about the match.
I can't think of a good squad-based game that fits the bill... but idk some kind of real time valkyria thing maybe. Both multiplayer and singleplayer are fine here.
I'd say foxhole, but again... such massive impermanence.
EDIT: or games where you can be a low level officer taking objectives? an LT? Captain? IDK.
Kinda depends on what specifics you're looking for; development and narrative can mean things like Spec Ops: The Line where there's definitely narrative and development with the small squad you're leading, but it's because that's how the story's written. It's not procedurally generated.
Bomber Crew has you working with a small team that'll advance and improve in their abilities, which tends to help with forming attachments just because of their usefulness and specialty, but all the mooks are by and large just bags of stats and items. The narrative you kinda have to come up with yourself.
I suppose the same kinda goes for Battle Brothers, but there they at least have a couple events that can fire off to make it look like your soldiers are interacting with each other.
Then there's Pulsar: Lost Colony... But that kinda needs to be multiplayer for it to work properly, the AI bot crew is neither particularly effective nor very personable. But the game's effectively Star Trek with more corporate overtones.
I also just remembered another game. Silent Hunter 3 (the entire series I guess). Much like the ARMA stuff, I saw SovietWomble play it. From what I've seen you play as a submarine commander during WW2, communicating and giving orders to your crew. It seemed like a campaign lasts a long time, so maybe it will meet your qualification of permanence.
Other sub games include UBOAT and Wolfpack, where UBOAT is more focused on solo play and Wolfpack is a crew sim that's best played with friends/idiots.