What if the movie starts off showcasing a well rounded mid early game squad, clearing out a UFO. Then the squad is deployed on a terror mission, and gets wiped out leaving a handful of Rookies to take their place, With maybe a single veteran from the first squad to lead them.
If it was established that xenonauts have nicknames, then ironically, the veteran's callsign could be New Guy, as he was once the greenest member of the squad, but now he's the senior officer. Mostly the film would be about trying to capture that feeling of losing your A-List squad and starting over with whoever happens to be standing around back at base.