I modified an old Burley trailer. I was going to modify it the way Adamdz did his, but took the easy way out.
I used leftover plywood and paint to make a flatbed, bolting it to the frame. I added t-nuts and bolts to hold the bin on. I can easily remove the bin if I wish.
I left the cage to attach bungees to. I'd like to find a stroller kit, so I can use it off the bike.