While busy researching something for a game of my own, I came across a thought I think I'll share:
Apparently dwarf stars are MASSIVELY underrepresented in our star catalogs simply because of limitations to how far we can detect them. If you add dead stars to this mass, it becomes possible that these could explain a quantity of dark matter as not being actual dark matter, but rather undetectable real matter.
Now if you have drives that operate by navigating using gravity wells, this potentially significant and constantly-changing interstellar debris could prove a significant navigational problem if it can pull ships out of hyperspace. Any actual collision is unlikely, since space is BIG... but scouts and explorers would likely travel to another star by jumping from gravity-pocket to gravity-pocket, staying in real-space only long enough to survey the debris and its gravitational effect, recalculate, then jump again.
This process would of course make interstellar travels much longer and more hazardous, possibly explaining lost ships. Once mapped however you should be able to bypass all this debris and simply jump directly to the target star.
Such a system would make interdiction and interception possible, as well as introduce a 'survey upkeep' (the debris don't stand still after all) and make long jumps expensive and risky versus shorter jumps.
Any thoughts?