I posted something similar elsewhere on a related thread (too lazy to go hunting for it to add a link here), but take "Shadows" as a for instance.
Instead of a bunch of newly retired characters fresh out of the Army, Navy, Marines what have you, how about a group of 18 to 30 year olds with skill - 0, skill -1, and maybe a skill - 2 for the ship's captain. Heck, maybe there's a pre-teen or a child in there as well.
Your ship is brought down by the ancient pyramid laser built by some long deceased reptilian race, and you don your HESes, rappel down the central shaft, come across some exotic atmosphere fauna, fire off a few rounds, avoid a few ancient traps, feel the earthquake or deep subterranean generators, shut down the laser, climb back up, and gain XP to applied to whatever skill you used. If climbing's a skill, apply XP to that. Hostile Environmental Suit gets XP. Whatever weapon you used against the local animals gets XP, and so forth.
You then move onto the next adventure. Maybe like D&D there's a warning for what skill level characters can do on the cover. Just my thoughts on the matter. I'm kind of all Travellered out. But, it's been a concept that I've had for a while.
late caveat; again, I don't like the XP-level system. It grates on me because it brings back memories of hack-and-slash players who played games for that as an in game reward, as opposed to playing the story, which is my thing.