Loop back is huge for content creators and I believe Steinberg would attract yet more clients with the addition of another loop back mode. Notably, podcasters who record interviews could edit looped back audio separately from physical inputs in their DAW without resorting to aggregate audio devices/generic drivers.
I believe either of the following possibilities for loop back would work:
Best option: Loop back to a virtual stereo input bus.
Ex: UR44C has 6 inputs (4 XLR & 2 Line). DAW would see 8 inputs (4 XLR, 2 Line & Virtual Stereo Loopback).
Alternative option: Be able to assign live cast loopback to inputs 5/6, allowing for a multi tracked 4 XLR + stereo loopback setup.