Literally tried using BlackHole with the same aim you do, but couldn't believe I was unable to route an input (BlackHole) to an output (DisplayPort, for example, in my case).
After hunting agressively on Google I was stoked when I found Apple's native, in-house solution: AU Lab.
I've also seen Source-Nexus, that has plugins for Pro Tools as well as VST/AU, and you can make multiple named drivers. It would work pretty well with Loopback it seems.
http://ju-x.com/hostingau.html