I'm working on that for the World Builder's Handbook. In fact, "Empty Hexes" is the last process I need to test before turning in the manuscript. There would probably be an effectively unlimited number of asteroid-sized bodies, but detecting them from a parsec or two out...
With the Harrier's advanced sensors about 4-12 weeks of scanning a hex 2 parsecs out, assuming a competent operator, but if there happens to be be a rogue gas giant out there (rolled secretly by the referee with the same likelihood as a star occupying a hex in that region (roll one check for large, two for medium {Jupiter is medium - superjovians demoted it} and three times for small) then they would be detected in much less time. A parsec-wide hex is a big empty place. Like I said, testing what I wrote. It looks good on paper, but it needs a little excel simulation to see if the process is practical in use.
Then there's the risk that it "looked icy" on scanners, but turns out to be dry. And the risk of a slight miscalculation in the jump distance leaves you needing one of them drives from Deepnight Revelation to move in deep space. Jury-rigged drop tanks might be the safer bet.