That's our coop. The box is 4x4x4, the nest boxs started 24" up and slanted down 9" to a 15" cut. If you only want four chickens, I think itd be fine to only have one side of nesting boxes. I have a door the opens half way up in the back part for easy cleaning. And it's completely framed, no insolation, but sturdy. If you made one similar with all the siding and shingles and such, three men lifted carried the co-op to be put on the stilts. I'd also recommend using a sled to move it around. That coop with six nest boxs, two roost bars at various heights, cost me under 200.
you only need 1 nest box per 3/4 birds anyway, use the other side for storage or do away with the time, materials and labor to build them and just leave them off