I've often puzzled that we beekeepers struggle so hard to prevent swarming and yet for the hive itself, swarming is success. Maybe we shouldn't be fighting it but using it. Here is a plan I am going to try this season:
Given a hive in swarm preparation, cells started, perhaps even sealed: Set a new box behind the original with entrance facing the rear. Move the queen to the new box on one frame with QCs and brood. (Make sure and leave some QCs behind in the old box.) Fill out the box with foundation. Now shake or brush most of the bees from the original hive in front of the new entrance. Over the next 24 hours, most of the field bees will return to the original box leaving the queen attended by young bees, which have never flown before.
Theoretically, I have now created a "post swarm" situation for both hives. The old queen in a new cavity with lots of nurse bees and lots of wax building to do. The old colony is queenless but has lots of cells started. Basically we jumped over stage two of swarming, the actual flight of the swarm.
The new hive still has QCs. I am thinking the new colony might interpret these as supercedure cells, since most swarms replace the old queen shortly after establishment in a new location. If my suspicions are correct, both colonies will have new laying queens at the same time.
Finally, do a newspaper combine at the honey flow. I discussed two queen hives with Sue Cobey and she made the point that a 2Q system is most successful with sister queens of the same age and pheromone levels. They will often lay side by side for many weeks.
I do know that my hives have a way with overturning my best laid plans. They rarely think like I do. But it is worth a try.
If this works, I can see an IPM benefit: no loss of brood laying and yet both colonies have a break in the brood cycle.