Are your breeders duos, trios, or a lot more at a time? How many different breeds at one time? You obviously cannot let them free range when they are isolated so whatever you build needs to be big enough for them during the breeding season. What is you purpose for isolating broodies? Is that just for incubating or will you also be isolating the hen and her brood while she raises them? How many broodies at a time? If you have power out there you could build in a brooder if that would be handy. A broody buster might come in very handy. A 160 sq ft shed means something like 10' x 16'. That space can be eaten up pretty quickly if you get very ambitious. You will need to plan.
Even if I knew a lot more about your plans I'm not sure what kinds of responses you are looking for. My general suggestion is to be as flexible as you can. My built-in brooder has a wire floor so it can be used as a broody buster it I need one. I can also isolate a chicken in there if it is not already in use.
Make it as convenient to you as you can. Think banging your head or elbows if you get in a tight space. Give your self enough room to feed, water, and clean. Where will you store feed? How will you water? Your comfort and convenience is an important part of the design.
I'd consider putting those breeding pens along a wall and build a run outside a pop door to house them. That could save you a lot of precious interior space. And it could give you grow-out pens or places you can use for look but don't see if you integrate. Broodies could raise their broods in there.
Good luck. That 160 sq ft sounds pretty large but for all you are talking about it may be kind of small.
