To the OP......I think the premise of what you would like to do, while I understand the concept......is a recipe for disaster.
First off......if you are free ranging in an area with even a normal predator load, the birds are already at great risk. Not a question of IF, but more than likely only WHEN. I have not included all of them here, but I'm now up to about 10 threads on the BYC predator forum that I know of....in just the past 6 months alone......all of which share the same basic theme......"help, my flock was wiped out".....followed by the words "I like to free range". Then it's on to how to stop a dog, fox, bobcat, coyote, hawk, etc, blah, blah, blah.
You stop them by excluding them from having a free shot at the almost defenseless birds to begin with.
To introduce yet another risk factor......an open access into what should be a secure coop offering 100% protection at night.......is simply compounding the felony. If I was indifferent as to the plight of my birds.......didn't care if they lived or died......I'd probably do what you are proposing.