I can't comment on the sturdiness because I'm not much of a builder. However, I don't think the recommendations for the wire are the best.
Hardware cloth (1/2"x 1/2") is not large enough for the bunny berries to fall through. You would have to clean it out regularly and it looks like it might be difficult, especially when there are eight or ten kits as well as the doe. A better choice would be 14 gauge welded wire (1"x 1/2") for the floor. It's much stronger than hardware cloth and more durable.
The wire sides seem to be made of 1" x 2" welded wire. Welded wire is good, but holes that size will allow raccoons to reach in and grab rabbits. They will eat them right through the wire, pulling them out a bit at a time. That size will also allow access to rats and weasels and possibly snakes. The largest wire I would use would be 1" x 1" and the same 1" x 1/2" I suggested for the floor would be much safer for the rabbits.
Better to spend extra money now than lose rabbits to predators later.
When I started with rabbits, I wanted to tractor them, but I soon decided it would put them at too great a risk. Instead I made a colony in our shed and gathered the greens to feed them. It was a lot less work than moving tractors regularly and the rabbits were much safer. I fed them a alfalfa/grass hay mix free choice and small amounts of grain as well as the greens.