Broad breasted hens do not make good broodies or mothers. They just can't move their legs and feet as delicately as the heritage hens can which frequently ends up with squashed poults. I have seen people claim that their broad breasted hens have broken eggs because of their weight but I suspect those cases are more likely due to a tom taking the sitting hen as an invitation to breed.I wouldn't mind hatching babies but only if it could be done safely. So I guess build a pen on a trampoline or separate them. Unless we can put salt Peter in the water supply