Ok we learned that building everythign out of wood is not going to cut ti and that the foam can't supper itself sooo I'm not trying to build structures that combine the two so that we can quickly deploy a medieval looking building for use as a game prop, but have it quickly able to be set up.
Tonight I tried to build an A frame building and it worked pretty well. I have the foam sheets on the frame and an now making the board / cobblestone cuts. Tomorrow I should be able to finish that and get started on the paint.
The structure is light enough that I can dolly it into position myself and we will fill in the a frame with sheets cut down the middle so you can't see if someone is inside or not.
I know this won't look the greatest but it will be a "lean to" kinda thing able to hold up against wind and rain. This is 4' x 8' and the picture above looks like a big sandwich board in this form. After the boards were together, I tossed the foam on with screws and liquid nails. The outside of the thin boards are frames in 2x4s as the plywood sheet was too thin to support itself. BUT in doing this, we then have the ability to toss some handles, chains and other things on the building.
We came up with some 10x10 designs, pyramids and some other things to make some different buildings all with the intention of quickly being able to deploy and retract them for public park uses.