Anyway, the feature is likely possible to implement.
The zebra code already looks for 100% white pixels; it'd be a matter of telling it to step down if it sees (m)any.
I've tried shooting_set_user_tv96(shooting_get_user_tv96()+32) and shooting_set_tv96_direct(shooting_get_tv96()+32, SET_NOW) (guess-copied from the bracketing code in shooting.c), but got awkward results - most importantly, the viewport's brightness doesn't change in real time.
But it's more than likely that some more clever functions can be employed instead, and/or a viewport update with the requested exposure forced.
