Leslie, when I saw this go by yesterday while I was on the road, my first thought was claymores or an open 220 circuit. Besides the liability, you would end up with a mess to clean up.
Seriously, the key to physical security is to make it just hard enough that the bad actors choose someone else - the corollary of "you don't have to be the fastest wildebeest in the herd, you just can't be the slowest."
The cage, as well as the suggestion to lag the AC sleeves into the framing from inside make the AC *far* more difficult to remove, and thus far more likely that thieves will move along looking for easier pickings.
When doing physical security improvements, I would make the mounting connections inside, or if they must be mounted externally, we would use high strength steel, then have the mounting bolts , once in place, welded to the frame. It means removing them will require specialized cutting tools that your average bad actor isn't going to have at hand.
Drop me a PM if you need some additional help. I'm not in the varmit hunting business these days, but I know some guys who know some guys.
