OK, shifts are on their way in, in some sense, at least for the military. But one thing I don't think I've seen specifically is this:
Sometimes you want some job or guard post or whatever manned, 24-7, with absolutely no gaps. You should be able to assign dwarfs to shifts for this position, such that the dwarf must not leave their post for any reason, whether drinking, sleeping, eating, going on break or even crawling off to heal - until their relief physically arrives in the neighboring square.
When the dwarf on station is entitled to go off - as determined by a time window, or by his getting hurt or some other rule or regulation - this signals the relief to drop whatever he's doing and showing up, highest priority.
The relief can do whatever he wants in the interim, though he should probably prioritize drinking, eating and sleeping more than usual, since he may not have the chance while on duty.
Of course, standing sentry without getting to sneak off to drink when one wants to is going to give bad thoughts. Also, all dwarfs will abandon their post under some conditions of thirst, hunger or nerve strain - depending on their personality. This is a crime, however, and may bring the Hammerer.
Regulations, such as shift patterns, severity of punishment, and whether it's permissible to enlist a nearby temp while you sneak off to get a drink, should be customizable by the user.