I agree, once and done is best!
70 chickens, 10Sq ft each = 700 sq ft minimum space.
A half acre is 21,000 + sq ft.
So, you can reduce pen size to help manage coverage, as one option. You could have a few smaller pens. You could create a mobile coop that gets moved to fresh grass once a week or something. If trailer is high enough, they can get shade underneath it and to a side that is shaded. Pen can be mobile and possibly covered easily, especially if mobile coop is a support for the roof/net.
The aerial predators are hard to deal with. It is also illegal to kill or harm a raptor in the US, so don’t go that route.