The situation is slightly more complicated than it might appear at first, because this year we've adopted a law saying that advantage from a knock-on hasn't been taken until you call zero tackle for the non-offending team. If there's some reason not to do that, then by definition there is no advantage and you have to go back for the restart.
What this means in principle is that a lot of teams are getting possession from a knock-on and immediately kicking and chasing, or spinning the ball wide quickly, and we're ending up with very prolonged knock-on advantages (and good luck working out where to go back to, 30 seconds and 50 metres later). Great fun, excellent for the spectators, but a bit hair-raising to referee.
So it's not beyond the realm of possibility that you could have a knock-on with 20 seconds to go (or, put another way, enough time left that, had you blown up immediately, they could have got 7 players and a football in position quickly enough to get time off and have a last play from the scrum base), the non-offending team (who of course are two or four points behind) spin it wide to West and go round the houses and there's three kicks and ten offloads and the ball eventually finishes by going dead in-goal.
(I still think that, in the absence of a clarification from upstairs, the answer is to end the half, but it's worth having a line of some sort ready to use in case someone complains about it.)