Would stacking 4-way mating nucs with a queen excluder between them be a viable system? This way the worker bees would be "shared" by each nuc until they grow into a strong enough colony to be moved into a 5-frame deep. Or is there something I am overlooking?
Orientation and return is the last of your worries.
Your colony , even though it is separated into sections and has an excluder is only a separation in
Your mind. In the bees opinion, if they can fully mingle, they are one colony and only want one new queen.
If you install capped cells the bees will usually tear down all other cells after the first viable queen hatches. (It's not just the virgins that do that) Also the virgin queens need
seclusion from any other queenright colony until they start laying well. After they are laying and well established, that is the point you can combine colonies through an excluder..
IF you are careful about your procedure.
If you install virgin queens in a multi queen, shared system you'll have a real mess of non acceptance. The first two things a virgin queen does is eat and kill. After she is mated and starts laying, she looses that killing instinct. AN excluder would do basically nothing to keep virgins from fighting through it.
I've even installed cells in double deeps with a double screened divider between the two. Checked for a hatch the day of, and found the top had a recently hatched queen, bottom deep's cell was torn down. No chance of that virgin getting through that double #8 screen divider. Both cells were candled before placing and close to emergence, so I knew they were both viable.
If that divider had been solid instead of screened, there would have been no issues. But if you are going to do that, why not have two separate deeps and easier accessibility?
I've watched bees tear down a capped cell installed in a queen right OB hive as well. Established Queen had nothing to do with it. I'll post some of those photos below.
That is what makes a newly mated queen (or a newly installed mated queen) so vulnerable to being killed if you leave the colony queenless for 24 hours before installing a new queen or cell. If you give them a chance to start queen cells of their own, new queens don't recognize 24-48 hour started cells as a threat and they are left to grow. Then the self started cell hatches and the new virgin kills the newly mated or newly installed queen.
(Everyone has their own way, but when I take out a queen, I immediately install the new queens, no matter if they are in the shape of an open cell, capped cell, virgin or mated queen.)
The only time I've experienced a multi cell successful hatch in a single colony is a swarm situation when the bees protect unhatched queens cells and virgins from each other in preparation for throwing multiple cast swarms.
As with many beekeeping procedures, the trick is timing and method details. Using
uncapped queens cells is a way I've found eliminated much of the destruction from bees in the colony is already queenright. This includes requeening and trying to replace an old queen without having to dig through the colony and remove her first. If the cell is installed and allowed to be nurtured and grow, it is received differently than if is is already capped and close to emergence.
Here are cells about 5 days old, being placed early in mating nucs because of a failed previous batch and I was short. These early cells have the same success rate as capped cells. You can't candle them before placing, but you got to do what you got to do sometimes.
Here is another cell from the same batch the next day, now newly capped