You will add a queen cell to a queenless hive and let it hatch and let the bees nurse the virgin queen?
I make mating nucs and I give a new born queen or queen cell to them.
How would you keep the hive strong until she lays? Just add brood frames?
Mating queen needs only one frame of bees. I raise queens in big normal hive which wanted to raise it's own queens - like for swarming.
What happens if the virgin queen does not make it?
Many things happens if weathers are bad. Have so much new queens that no problems if something happens. This year I killed some new queen because their descendants were too hostile.
For winter I have united small nucs. It is better to unite 2 equal size colonies. Two week colonies together and unite then them to teh stonger colony to reach one whole box of bees. So they do not kill each others.