I don’t see this working.
You finally abandon trying to ignore the full bladder because you would actually like to sleep a little, so you push back the quilt, unzip tent inner, locate TP, swerve round to get feet out of inner ready for upward hauling of body ... and at that point, probably feeling time and other pressures, you scrabble around to find poncho head hole, lift over head, bang tent side walls causing cascade of condensation, start the hauling body up process (late) with the bulk of poncho around you making it trickier to avoid vestibule walls, position p-bag, bottle, pot (whatever has been decided upon) *under* the generous poncho flowing around you, without tipping pot or wetting poncho and get up without poncho knocking over the sacred vessel.
I think not.