I haven't thought much about it honestly.
Perhaps we can add a KCM page like night-light? I can add some curve controls to map the ambient brightness to a target screen brightness.
Another option is to have a simple on/off switch with an adaptive algorithm like android or wluma that learns what brightness you prefer for different conditions.
I would like to see all screens with brightness support be adjusted, although this may need a per-screen-type offset to account for different screen luma ranges.
I'm really open to anything, I expect to be chipping away at this problem for a while.