I'll try to answer everyone one in this post
3 things in a coop shelter, roost, protection
PVC can provide for all three just by tweaking the design of it.
Most of the concerns were about protecting the chickens. Now I've got mine in the backyard so my worst predator is a cat or possum.
By using 2X4 and chicken wire together you can stop just about everything from getting in, using wire to attach the fencing to it will help stiffen everything up a little.
You can put sand into the pipes to give it more weight or I've read that someone actually used concrete that should help with something lifting it up.
Also if your really afraid of something coming after it you can increase the piping size.
If you on a huge farm and have had problems with coyotes, stray dogs or anything bigger I might not use PVC. You might wake up in time to stop whatever trying to get in the coop but you may have to rebuild it.