Hi Anna,
This plan and goal set is admirable. Similar to Andrew's observation, I would (and do) always say look to the "vernacular forms" of a region first, then perhaps to similar climate regions of the world and the vernacular of those cultures. Instead of looking for a "coop build," I believe this
project would be better served finding a
local "traditional builder" to work with. Unless the proposed "co op partner" comes on board with advanced skill sets and understanding in architecture...well...it often can lead to challenges in the "vision" each party has...and understanding who is responsible for what level of "skill."
I have "little projects" all over the globe at this point that I am lending a metaphoric had to. My other observation is that 1 acer is really a small space unless there is "common ground" open to residents of the area for "permaculture" endeavors. I would say for something like this project with independent parties, it would seem 2 to 2.5 acres would be a bare minimum, unless the only goal set is a "natural build," and "house share," potential.
Please keep us all up to speed on the progress of this project, and please post pictures when able. Questions and thoughts are always welcome.
Regards,
j