I commented earlier on github. Alas, since then I've abandoned TVHeadend after many years, mainly as I can't get either a usable USB DVB-S2 tuner or a Sat>IP router (I've had to return one of each; a Hauppauge device that no longer works with Linux despite claims to the contrary and defective device that I don't want to try again because of apparently high failure rate).
Accordingly my tvhplayer is kaput for now unless and until you make it work with my Enigma2 boxes. The killer feature (for me) that I was hoping to use was an ability to select the box and then use the EPG to schedule a recording.
I don't record that much but it does happen quite often that I need to make simultaneous recordings on different boxes.
Perhaps one way of looking at it could be: one EPG and an ability to indicate with a right click, say, which box to record something on -- instead of selecting boxes first and scrolling through separate EPGs.
No need here for separate user profiles.