I played around a bit more with it. Apparently, while it's not yet possible to apply any volume or panning before recording a loop, it's available as soon as a recording is CUEd. This is good news, as it allows to create a MIDI binding like:
(Assuming CUE is toggled on, input is set to 1+2, and the clock is set to the wanted length)
For q:
- Go to loop 1
- Record
- Pan hard left (mic)
And for Shift+q:
- The same, but pan hard right (guitar)
And for Alt+q:
- The same, but without panning (recording both mic and guitar)
For, w, Shift+w, Alt+w, e, Shift+e, Alt+e, r, and Shift+r, Alt+r, similar bindings (for loop 2, 3, and 4) could be defined.
So for me to make fast and reliable switching between inputs possible, only the "Set pan to X" binding for keyboard needs to be added. Sure, a "real" routing would be even better, but the explained workaround would bridge the gap until then.
Combined with bindings for jumping between groups (~ for master, 1 to X for group 1 to X), with only a few keystrokes I could switch incredibly fast between groups, loops, and inputs.