It reminds me the early days of Bhajis loops when Olivier, the developper, was trying to get this ***** timeline cursor running in the pattern editor, he said it was *the* worst memory hog ever, and finally gave up on displaying it. The usability did not suffer as much as one would think. AFAIC, the most important kind of accuracy we need is *audio*.
Of Course visual accuracy is nice too, but more when "editing" (I like your "trim at playhead" command very much, BTW)

I played with an Android (based on this cpu) phone for 2 weeks, and tried an app called 16 bars, the interface is *very* minimalistic : Just a static screen, you only have the sound of your first track to cue the second one in, but it works. I tried recording a metronome on track one, loading it in the app (yes, you cannot even record *two* tracks in it, just one over some existing mp3) and recording another one, the tracks were nicely playing along.
This was actually the first time I did successful re-recording on a palm-sized battery-based machine.

All this very-remotely-english verbiage to say : If the display must blank completely while I'm recording something, it's fine with me.

I have a tendency to sing and play w/ my eyes closed anyway

This app is going to ROCK, I can tell