So I have a completely crazy idea, that might just work. Bare with me because this will be lengthy.
I moved the 8 and 9 week olds to their new run, which means the 9x18 run is currently unoccupied.
The 9 older birds have been roosting on the stair railing near the henhouse since Sweety has been sitting on eggs (yes it's a mess, but I don't mind since they were keeping her company).
I have this 'chick hut':
https://a.co/d/hoCPYoP
and two of these 'chick pens'
https://a.co/d/1BrM86f
I usually use them all connected end to end to integrate chicks and it works really well.
I'm thinking I can use this setup with a bit of hardware cloth between the two pens. One side will have Sweety and her brood, the other will have the incubator chicks. Since the incubator chicks won't have access to Sweety, initially, they'll get the end with the chick hut. All of this will be under the cover of the 9x18ft run. It will look a bit like this:
View attachment 4210849
View attachment 4210847
These are pictures of how it was set up a few months back, but I'll get new pictures tomorrow when I reset everything.
Here's my thinking; if I setup feeders and waterers on either side of the divider and they all can eat in close proximity and the older chicks aren't able to harm her chicks, and she can't harm them she might just accept their presence, even if she doesn't completely adopt them.
If I see behaviors like her calling to the older chicks, or sleeping near the divider to try to provide them warmth then I might try letting her in the run with all the chicks and see what happens . . .supervising the whole time of course. While I'm doing this all the other chickens will be outside the run, so they can't interfere.
I figure, worse case scenario, I'll have already started integrating the incubator chicks and keep them in the pen until they're about 4 weeks olds. (That's the youngest I'm comfortable putting young chicks in the same space with the older birds if they don't have a hen protecting them)
I'm also hoping if the older birds see the incubator chicks "in" the pen with her, they'll assume they're hers (which most are, but you know what I mean)
Ok, I'm rambling . . . and I'm not sure much of this makes sense, but I'd like to her y'alls thoughts. Is this idea crazy enough that it just might work?
ETA: Another 'worse case scenario' option; I could move one of the chick pens and the hut to the run with 8 and 9 week olds and integrate the incubator chicks with them.