Yeah it would be cool if you could draw the plan and then it could generate all the wall and roof pieces! It could work like @jestelle’s drawer dividers generator.
Next time I take a look at this (tomorrow?) I’ll add support for an overhang (on the sides and the front) and will parameterize it based on pitch instead of angle as @yoyodyne2112 suggests.
One question: do you generally glue these pieces together or use finger joints? Your box-o-matic mention makes me think finger joints but it looks like @timmystreehouse’s designs (which are awesome!) just have faces glued together…