I'm pretty sure this has come up here before as well, but does anyone on
the list have familiarity with USB controllers?

Given that USB is a more general purpose bus than ATA, having a Qbus to
USB bridge would be useful for a wide variety of devices.  Everything
from disk drives, CD burners, digital cameras, scanners, printers,
ethernet devices, etc. could be attached to our old VAXen.

-brian.