Sometimes I love messing with bad people. I never do anything that will cause harm but messing with their mind is great fun.
If it is going to stay at the lease, how about removing the king pin assembly. Better yet, find an old one (junk yard) have it modified so the pin is way to big to fit a hitch or just ground off the pin. They show up to take the 5ver, and find out it does not fit the hitch, or there is nothing to connect to.
Have any really good buddies that are fabricators? Have them make up some square wheels for the 5ver. Could fabricate them out of steel (fill with sand, concrete, mineral oil, etc once installed) or a wood form to make them out of cement. Have proper hubs in them to bolt the square wheels to the 5vers axles. Great conversation point for visitors. Thieves may just shake their heads and leave. Might take pictures and post on facebook too.
Chain and cable locks are fairly easy to get around if you have the tools or knowledge. Some are much more difficult. Usually the lock is the easy item to bypass, so make sure it is difficult to access, even for yourself.
I have a couple buddies with hunting land up north. Most have issues with trespassers. Most have at least a few trail cams installed. All of them, say they now use the expensive lithium AA batteries as they can get about 1.5 years out of the batteries. One buddy has a couple of older cheap trail cams in plain sight, but mounted in a harder to get to. Then have a couple of their better ones that can see those cameras and able to capture the vehicle information along with passengers. I think Scott has about 8 cameras at his place. Few placed just to get license plate numbers and images of people walking up the road. He has big memory chips in them. I think he said for most part he swaps out the chips about 3-4 months unless he notices something when he arrives. I believe they all have camera on premise signs up along the drive entrance with no trespassing signs, to help scare the riff raff. They still get a few who come onto their property. I think Scott also drive some massive well casing pipe down on each side of his drive, and uses an extemely heavy duty chain now. I recall him having issues when he was using a light chain/cables.
I like tire boots. Not sure about the ones on Amazon. Had some great ones when I worked security when in collage. Heavy duty, quality lock mechanism, with a bolt behind it that you needed a large socket to release the clamp. We had many people try to remove them, or try driving off with them on. Never lost one, none were ever damaged, cars on the other hand never were the same again.
Personally, I would hate it if they just broke in and did damage more than stealing it. I suspect I would install a hidden GPS tracker, connected to a solar panel to keep charged. Set up so it sends a signal if the 5ver moves more than say 1/8 mile. A few well placed trail cameras, with signage as someone enters the lease. Maybe even one on the king pin, reminding them to smile as they are on camera, even if I did not have a camera on the camper.
If a thief wants it, they will take it or damage it
Good luck