Longer answer is that I haven’t been able to find things that are too compellingly different. You can’t come up with every backstory so I don’t know where to start looking for holes. Maybe we can start collaborating on this thread?
Maybe a systematic way is to look for holes in the Discipline bonuses? Right now there are three Environments that give bonuses to Command, Security, and Science and two that give bonuses to Conn, Engineer, and Medicine. It seems like a nomadic life on traveling starships could fit that second category so that works! Likewise, there are four Upbringings that give bonuses to Command, Conn, Engineering, and Science while there are only two that give bonuses to Security and Medicine. I think Conn could also get some love so maybe an Upbringing of Mercenaries or Criminals that could give bonuses to Security, Medicine, and Conn?
As for specific niches like the Bajoran Occupation, I think those are best handled in species-specific sourcebooks. There are certainly more character creation options that could happen with Bajorans as well as Klingons, Romulans, Vulcans, Trill, Ferengi, Cardassians, etc.
Would it be possible to create life path options around characters who were raised in different factions/universes and later converted to starfleet? Our would it be better to just try and reskin the starfleet career path?
I think the best option there is to reskin the Starfleet career paths but you could change the name and shift things around a bit. I have plans for new upbringings and environments for other factions, but they don’t need as much work. The Career Events table is where I’ve introduced the most changes.