I explained in some detail previously that for my second chicken tractor, I lowered the nesting boxes. As I noted in another post, the original plans have the nesting boxes relatively high in the tractor which made them the go-to roosting spot. To this day, my older birds try to pack themselves into the two nesting boxes each night to sleep. That's problematic on a number of levels. First, it has dissuaded them from laying eggs in those boxes. When they started laying, I put another nest box on the floor of the tractor and they have mostly used it.
Another problem is that there's a lot more stress on the nesting box framework than anticipated. It was really only designed for one or two chickens to be there simultaneously, and for relatively short periods of time. Instead, it has 50 pounds of chicken sitting on it all night, every night. I added some bracing but it's holding up relatively well.
So those were the factors that led me to modify the second tractor. I introduced a lot of complexity but can confidently say I successfully removed the nesting boxes as a roosting spot. I kept the boxes closed off until the new chickens started laying, but now that I have opened them up, there's very little evidence they have been used at all. I have only gotten one egg in the boxes. The rest end up like this:

You can see that they have all decided to use the same spot, back in the sheltered corner under the nesting boxes. You can also see hay, which has been used to hollow out the nesting spot. I've been using hay for bedding in the tractor for the last few months while everything has been dormant. I can't move them around on the grass when it isn't growing, or they will over-graze it. Hopefully, once things start moving and they are on grass, they'll decide the nesting boxes are a better place to lay eggs. If not, I'll be 0 and 2 for nesting box placement.
Overall, despite the spot being relatively tough to reach, it's working pretty well.
Update: In the last week, I have started rolling them around the yard again. They are mostly still using the same spot, in the back corner sort of under the nest boxes, but there are usually one or two eggs out in the middle of the tractor, too--that's bad, because they're susceptible to getting broken. Sigh.