Long term use tractor/run design help?

Koi's current enclosure I made independently and is just 1" X 2" held together with stapled and prayers, wrapped in wire. I was very determined to do this project on my own, and it shows. Now that I have more expiriance building, I jwant to make it a bit more solid and maybe add a lid that is actually attached, ya know, just the basics lol

It can't be any bigger than his current one which is 6' X 2' X 2' both for ease of movement and space available.


Bellow are some of the ones I've seen that I've liked the designs of. I really like the last photo as it appears it could be put on the ground or elevated.
He will be under the carport/barn primary, but I do like to move hime to the grass when weather is good, so something with a proper roof would be nice (not 100% needed though, just a wire lid is fine too), and obviously sturdy enough to withstand the moving

If anyone would be able to share some picks of there tractors, tell some trial and error stories/what's worked best for you, what to stay away from at all cost, or any other tips that, would be great.

Whatever I decide on I will be building this one with a little more thought, research, and willingness to ask for help than his current one.

you will need to provide a shaded area of some sort so he can get out of the sun. Any of those designs will work but may I suggest you build something that the whole thing isn't a lid? Having a top lid in the middle (make as big as you need so you can reach all corners) and that you can latch down (with latches critters can't open). Build it out of sturdy wire (again for critters).