An astronaut a radiation wave hit that got shot through a wormhole, now lost in some distant part of the universe on a ship, a living ship, full of strange, alien lifeforms, while being hunted by an insane military commander, doing everything he can, just looking for a way home ....
In all seriousness, I'd like a non-military role, and if it is a military role, have the option for the PC to not be that thrilled about it. I'd like the option to choose one of three backgrounds, surveyor (such as a cartographer, geologist, town planner), who determines how well a planet will suit colonisation, technician being team support, with roles including medic, engineer, drone operator etc depending on class - essentially making sure the expedition team is running at peak efficiency, a some soldier/security/mercenary type for the people who just want to shoot stuff and blow excrement up - they get no story or narrative advantage like the others would, but get a boost in combat skill spending. Expedition leader, not captain - in what universe is it logical to send the captain, tactical officer, chief medical officer and chief engineer on a risky mission?
Though if they are going for the whole Western frontier thing, they could have typical western roles such as miner, merchant, doctor/medicine woman, schoolmistress, brothel madam etc and the game is essentially Oregon Trail IN SPACE!