Interesting ideas!
I'm not quite envisioning how the pvc-hooped top is going to attach to the wall T-posts? Without making the whole thing twenty feet tall, that is. Or do you mean you're making a normal pvc hoop house (where the arcs of pvc go all the way down to ground level, anchored on posts sunk in the ground or at least on a 4x4 or 4x6 laid along the base of the wall) but are putting a t-post-and-wire-mesh fence *around* it?
Like the previous poster I'm also thinking you're going to need to give some thought to wind resistance -- it looks to me, from what I understand of the construction, like the sort of structure that just a moderate-strength thunderstorm could seriously disassemble. At the very least, your tarp will leave every time you have a storm, possibly taking bits of structure with it, because it will flap and because the wind can get under it so easily.
Nest boxes should not be a problem, though, youre just going to have them freestanding or built into the tractor portions, I expect?
Pat