Hi, Al.
I have three tractors, and my newest one I have a door on and wheels on the back for easier moving. I know what you have in mind from the Okies thread and you might want to repost it here for more input so folks know what you are talking about. I have no thoughts on that since it is out of my league, but I can tell you how I use my tractor, and how I plan to next season.
I personally use my tractor as a mini-coop, so it doesn't matter where my coop is in relation to it. Before Spring chicken season I plan to get some electric netting for added predator control and work as a free range area for my birds. I will start them in the brooder and after they are feathered out they will go into the tractor. They will stay in it 24/7, with the netting around it, until I am confident they can't slip through the netting. I will move it the same way I did this year, by slowly pulling it forward. Since it is only 8 feet long that only takes a few seconds. When they are big enough and used to the tractor as "home" I will open the door and let them free range inside the netting. I will still move the tractor, although not sure how often, and move the entire setup once a week.
Since the perimeter of my property is now surrounded by electric fencing, I will run my netting off of that. Don't have all the logistics down for that, but a lot of folks use the 12 volt battery type energizer, although that's not an issue for me.
I know you have a predator problem out where you are. For that I have my four dogs and electric fencing, running at 3 joules and 15,000 volts. Accitentally touched it and my fence the other day and it about knocked me on my rear.
My meat birds will have the added protection of the electric poultry netting.