I think it comes down to us working with them either way.... hopefully even a broody hen was well socialized so her letting us work with chicks wouldn't be an issue AND the plus is that the chicks would already be socialized with the established flock (and that's HUGE). Obviously socializing...
That's exactly what it takes... all kinds of socialization. Besides, our first 16 hens were rescued from a farm and came to us naked as could be and the lady had never handled them other than to shove them with a thick leather glove. Here, just months later, my children (7boys 2 girls) can...
I can only reply based on my years of experience raising exotic birds. I have generally chosen not to incubate because hens were created to raise chicks.... they keep them perfectly heated, humidity controlled and fed once hatched - *generally*. Of course there are always some not-so-great...