I wouldn’t let a disabled hen sit to hatch chicks. But thats because I integrate them after a week.It’s rather large, for a large dog. Mumma hen is disabled so she can’t move around easily, but the chicks have plenty of room. There is no run attached to it.
The chicks need more space after a week or so. You need to build a separate run because if the disabled hen , she can’t defend the little ones.
I don’t candle from 12 days old. And always leave the eggs with the broody further on the proces. She comes off the nest to eat, drink, poop and take a quick sand bath in her own time frame. Interfering does more harm than good imho. Touching the eggs much or cool them at the end of the hatch is not good for the hatch. In general the broody knows best.