
So, what if there was simply more variety in system composition and size? Say you had, every now and then, an absolutely enormous system with a really bright star, and intra-system gates linking various portions of it together? And then you had little tiny systems around remnant stars and nothing outside a certain radius except really crazy evil enemies who breathe vacuum, or something.
That kind of variation might be more interesting in the long run than either more, smaller systems, or fewer, bigger systems.