What I meant was that each star system should have a distinct nebula (or lack thereof) background that shouldn't change from one mission to another within the system. Because of the vast distances of space, the relative positions of the nebulas wouldn't change so long as you remain in one system. Planets can be changed around within a set background pattern, but they should not be used alone to define the system.
As for binary/triple systems, those should be avoided unless it makes the system true to reality. For imagined systems this doesn't matter, but almost all of the FS systems are real (I don't know what Vasuda is supposed to be though). Alpha Centauri should be a binary system (unless you count Proxima Centauri, which would make it a triple system), while Sirius should be a single star system.
