So my understanding with your idea, @Lotherio, is that all of the players are in one ship. What if Bob gets tired of where Alice is going and wants to hop on a different ship at the next spaceport?
This has always been my hesitancy with spending time working on a space truckin' MU* - the likelihood of the playerbase fragmenting and scattering among the many planets, so that there is no interaction. This would be perfectly fine in a MUD environment, where people tend to do their own thing with the automated systems and only occasionally run into one another. But then again, I don't see much difference between a space-truckin' MUD and Eve Online or Elite Dangerous, except Eve Online and Elite Dangerous have better graphics.
Whereas the spice road idea or the island world idea with airships I brought up a while back have a much smaller scale and it's easier to concentrate the playerbase into space where interactions are more likely to happen.