Nice spacious loft. Only thing I see deficient is the predator proofing. A raccoon can rip thru chicken wire. I would add a second layer of welded 2 x 4 or 2 x 2 welded wire on exterior. Bottom 3 feet all around.
You could use a loft similar to the ones I'm including pix. These belong to
backyard pigeons
You are going to be keeping 20 pigeons plus whatever little ones add to population in coming time.