Here's my plan for a rabbit hutch/worm bin combo. It's pretty sketchy, but I know it works. I'd love to here from anyone who trys it.
Rabbit Hutch with Worm Bins
Basic Rabbit Hutch
Cover the bottom and sides with 1” x ½” 14 gage wire mesh. (DO NOT use chicken wire. It will rust out very fast and it will hurt the rabbits feet.)
Make a door in the front and solid sides if needed for weather protection.
Make the top extend out beyond the front and side edges to provide weather protection.
Cut a board ½ the size of the bottom to provide a solid place for the rabbit to rest. Do not attach this board to the bottom. You will move it from one side of the cage to the other every two weeks.
Build a box 16” deep that fits at ground level under the rabbit hutch. Make the front removable and divide it in the middle with wire mesh like you used for the rabbit hutch.
Fill the box with damp worm bedding. (I like shredded leaves for this but use what ever you have that is suitable for worms.) Add worms.
The solid part of the hutch floor protects one side of the bin from most of the rabbit droppings. When you are ready to harvest worm castings remove the top layer of worm bedding from the covered side and add it to the other side. Remove the remaining bedding an inch or so at a time allowing the worms to move through the mesh to the active side of the bin. Screen the castings and refill the bedding.
You may need to add more bedding or dampen the bedding from time to time.
You can add kitchen scraps to the bin on the active side when ever you want. I recommend covering them with a bit of bedding to keep unwanted pests out.