The problem I have had with the wire floor is that it tends to smush the grass down so the rabbits can't get the full benefit of it. I had better luck with the larger wire (1x2 instead of the 1/2x1 that most cage floors are made of,) but it still didn't help with the larger plants like dandelions and fireweed that have the most nutrition.
Joel Salatin used rabbit tractors that have wooden slats spaced about 2 inches apart. The people at Weathertop farms (
http://www.weathertopfarm.com/id69.html ) tried this and decided not only were the rabbits not getting optimum use of the pasture, but it made the pens very heavy. They say they have had so-so luck with a modified version that only reinforces the corners and sides for digging, but it isn't fool proof. Also, for this you would have to have very flat pasture. (Which I do not, personally!) I think even these guys eventually gave up on pasture raised rabbit because it was just too labor-intensive, but if you only have one pen going at any time for your own use, you could probably make it work.
I've researched it all a lot. Pellets are expensive here and so is cage wire. Putting rabbits in individual cages makes my work-load unbearable in the winter due to freezing water issues. I have a lot of incentive to figure it out, but the bottom line is that rabbits in wire cages on pellets always end up in the best condition the soonest. It's fool-proof, proven, and reliable. Still, I keep experimenting because A) watching rabbits on pasture and in a colony is just more fun and B) cost and labor make colony raising much more desirable. I have my larger meat does in a colony setting, but my show rabbits stay in cages. I cut my pellet cost by adding a lot of locally available grains and hay, and in the summer they get all the high quality weeds and garden scraps that they can eat, but I have completely given up on a more traditional "pasture raising" model due to escapees and the difficulty in maintaining condition and grow-out.
