I think most chicken keepers have these types of problems. I have two maternity units which are in many respects outside brooders. Sitting and hatching in the coop has a lot of advantages for hen and chicks. The tribe get to know the chicks and the chicks the tribe from day one. There are no integration problems. When the hen takes the chicks out of the coop they have the option of following the tribe. This is also good but not all do.Wow, reading about these challenges I can see why people use brooders. But that's not really an option for you. It's very challenging! I hope the folks in your chicken club have some suggestions for you.
My view, I realise it may not be popular with many people is losing chicks one way or another is likely and this is in truth how a feral population is controlled. Hens lay and hatch clutches because the survival rate is low compared to say a mammal.
I don't mind losing chicks. What I don't want is to lose a mum because she defended her chicks. I've lost some great hens this way. Most of the hens here will go broody if you show them an egg so they can lay and hatch more chicks.