This is what I would do.
I would take one side of the barn and make all ten of the pens on that side. Every pen would be 3' wide and 5' long so that all 10 pens are in a line. As you said each pen would have a pop door to an outside run of 3' wide to as long as possible. I would have have the feeders and drinkers all on the close side inside the barn so that they could all be serviced quickly and easily. The roost bars would be in the middle. Each pen would be about 5' tall with a full side door from the inside and divided by a solid wooden divider up to about 3' and hardware cloth for the last two feet.
If that plan was used each pen would comfortable hol a trio or pair or even a quad at a push. All the daily chores could be done easily from the inside. Just how I would do it.