You have picked up on a very complicated subject
@Elowen. The perfect coop doesn't exist as all the features become compromises to satisfy other features. To be avoided is a coop designed for ease of manufacture, because invariably you end up with something quite unsuitable and a good example is Omlet who have designed theirs around a manufacturing process with perhaps no experience of keeping chickens, ending up with something quite unsuitable.
I've made 10 coops. The first was terrible and was left in England. The second needed a few modifications but was generally OK. The advantage of wood is the ability to repair and modify, but unfortunately the quality of wood sold today is disgraceful. Two have been made using old sheds. The floor and roof is therefore stable and the framework can be disassembled and because it is seasoned will be stable. There is a mobile one built in 2012 on this forum.
Ventilation equates to 10% of the coop floor area minimum and needs to allow cross-flow overhead. Chicken hate draughts as it disturbs their feathers and removes their natural insulation. Ideally the vents should be adjustable, so in a strong wind one side can be closed down. In Summer they need a large airy coop and in Winter a small one so they can squeeze together for warmth. Filling a coop in Winter becomes overcrowding in Summer.
The most important factor from a keeper's point of view is the coop floor height. Ours are set at 18" with large doors for our access. This means the coop will need a 30 degree ramp or 45 degree steps for the chickens to enter. We poo pick daily (or I do). Essential bedding is kept dry as mould spores will develop in damp bedding quickly leading to respiratory infections, particularly if ventilation is poor if only due to a lack of breeze.
A walk-in run is a real benefit for daily water changes, feed topping-up and poo picking. Ours are not because they needed to be light enough to move about, and then disassembled to move to France.
Foxes are everywhere, although you may not see one. We had one patrol our coops every night looking for a way in (careless door left open) as the footprints were visible in the snow.
Coffee time!
