My headcannon for this is that spaceships in that universe are to those people what cars are to us. If you know the basics of driving a car, you can drive most cars, though the bigger ships might get more complicated (I’ve never seen one of our heroes try to back up a star destroyer into a starbase to help with their buddy’s move.)
I don’t like the idea of restricting the model’s corpus further. Rather, I think it would be good if it used a bigger corpus, but added the date of origin for each element as further context.
Separately, I think it could be good to train another LLM to recognize biases in various content, and then use that to add further context for the main LLM when it ingests that content. I’m not sure how to avoid bias in that second LLM, though. Maybe complete lack of bias is an unattainable ideal that you can only approach without ever reaching it.