Hi Jeff
I've just consulted my notes to ensure the below is correct.
Last year on September 28th, I united 2 six frame colonies into one national BB with a newly raised and very prolific queen, so they'd be fit for winter. I wanted to keep the second queen as insurance, because although she'd not been my best (daughter of my best), she was also newly reared and was laying pretty well. I couldn't spare enough bees to make a national nuc viable, so I decided to experiment a bit with a 6 frame dual (1 x 6 or 2 x 3) poly mating nuc, to see if I could use it to park a small colony over winter.
I'd strapped the tiny frames into standard frames and had them placed at the edges of the brood nest in both hives a week earlier, so that by the time it came to do the unite, 4 were fully drawn and holding a bit of stores. These came out and went into the nuc, along with the spare queen. I then shook some bees from the hive that was going out of service, onto a sheet and board, leading to the entrance of the nuc. Within 10 minutes, all the bees that were going in had gone in (probably around 1000), and I left them to it.
A week later, I checked the nuc and found that 2 frames were fully laid up, with pollen going in rapidly and a lovely miniature arch over the brood. The other two frames were filling with stores and the bees had drawn the 5th, and were stashing nectar in it.
Other than feeding 2:1 and giving them some nektapol/neopol early this season, I left them alone. They're doing well - slow but sure - and will probably be fit to burst out of the nuc within the next 2 weeks. The 6th frame is fully drawn and filled with stores and at last count at the weekend, had 4 frames of bias (2 wall to wall and 2 about 50%).
I think I'd be rather more inclined to do it this way than the way you hypothesise, but even with an atrocious winter/spring like the one we're still lamenting, it's possible to bring a tiny colony through.
Cheers