I have a tractor that I haven't used for a few years. It had a 1" square wire floor in it which I removed.
I never lost a bird to preds in that one.
If you feel you need a floor in it, why not go with large squares, and then along the edges add a layer of smaller squares for about 6 inches in ? Or make a flange around the outside perimeter with wire mesh ..
I think having a floor in the tractor sort of defeats the purpose of having a tractor. A tractor should allow the birds to eat grass as you move it around the yard ..
otherwise, isn't it just a coop ?
JJ. go ahead and get the peacocks ..