You could also build a communal nesting box.We have one that is 3 feet long,18" deep and 18" high.See pic below:
Once DW said we had 6 birds in there,jammed to the brim.They were not in even rows,but frontways,backwards,and even sideways!!We can acess it from the outside of the coop.

Once DW said we had 6 birds in there,jammed to the brim.They were not in even rows,but frontways,backwards,and even sideways!!We can acess it from the outside of the coop.