I've put a large plant saucer of sand in with pullets, in their tractor. They needed something larger after they got bigger, but by then mine were free ranging for the summer.
In between being locked up all the time as chicks and free ranging all day as larger pullets, they went through a stage where they were only out for lesser amounts of time and supervised. They always went for the big dust bath I set up for them in the yard. After that, they foraged, scratched and drank out of the dog's water bowl. They didn't do much scratching in the tractor, they saved most of that for their daily outing.
The other thing you could try, is giving them a bit of time right before dusk, to get out for a nice dust bath in a full size dusting area and a little foraging. It might satisfy some of their needs outside of the tractor. Once we started free ranging, we rarely had to even move the tractor. When they were totally confined, we needed to move it every day or two. Even if you only let them out for a little while each day, it might help.
We have deep snow here now and the chickens are in their winter coop, with a partially covered run. We put a big rubber tub of sand in their run and even though they aren't dust bathing in it this time of year, they mess around with it every day. It's the size of a patio table. They climb in and out, scratch around in it and roost on the thick edge of it. So, maybe a saucer of sand will help you out, by giving them something else to do.
If you end up using wire on the bottom, you'll need to either lock the chickens in the housing portion or let them out in the yard to move the tractor. Otherwise, you risk the chicken's feet getting injured.
I'm thinking you should just try a couple of different options and see how they work for you.