I don't think in-game will buy "passenger" really, in a nation-simulator, maybe less so than shareholder, as at least you can argue in a modern-tech or sci-fi setting that nations can be shareholders in a mega-corp. The CU at least had member worlds that were basically nations, which was more in line with the sort of game that Nationstates is, so I'd argue that it is better than this or LazCorp in that respect.
Sort of has the same issue LazCorp has as far as the "shareholder" being not equivalent to a nation-state as such.
You could try it, though I think that folks could be confused by the concept of being on a single spaceship versus having whole fleets of spaceships, with planets around that theme. I can see this as being the real stumbling block with the concept.
Any ideas?