John Jameson McCarthy:
As for the fence, would building structures at the corners that could be manned help. I can't remember the name now but little redoubts to cut out blind spots like the Vauban Forts?
A redan? I believe they would work. If you built bunkers at the corners, out/away from the wall, they could have wide LOS to keep the wall clear of attackers. The wall has holes, plenty of them, but you can't really see well through them or have a clean shot unless you are right up against it. A tunnel beneath the wall could provide access to each one.
There's also concertina wire to think of. It's a quick method to deny ground as well and isn't a serious burden on manpower to set up... though it doesn't help much if you are concerned about vehicular attack.