Here’s a brake configuration that I had never even thought of. Sycip Designs put a disc brake caliper on the down tube which grabs a rotor mounted to the left side of a special White Industries crank. Since the rear wheel is directly linked with no freewheel to the crank, stopping the crank stops the rear wheel. Kinda odd, but you would never have to worry about disc/caliper alignment while adjusting the chain tension and you would use a normal track hub. But I think you’d definitely want a real track hub with a reverse-thread lockring.