So true, so true.
Between securing the top of the coops/run from hawks and 'opossum and the underneath/bottom from coons, seems endless. Also secure doors/windows/locks.
We mostly have open air for sides (fenced with chicken wire and lots of hardware cloth. Use tarps or wood panels for sides due to inclimate weather. Tin roofs. Everything under trees as much as possible for shading. Ventilation, ventilation, ventilation here on the Gulf Coast due to heat and humidity.
Last year even had to put a big circulating fan in the coop area to move the air around, between the pens, just so I could tolerate working out there with the birds etc.
All of mine is out in the open so a fan in the coop is probably the next order of business. The extended forecast is for 90 degree plus temps in a couple of weeks so I'll have to get off my duff and get busy.