I've tried letting my students make decisions in classroom layout and design and it has been successful. They seem to be more comfortable because they had some input. What if this was taken further. What if students built their own classroom?
An indoor or outdoor area that students create from the ground up. Multiple subjects can come together to create this. Business/Math can handle the financial aspects, Construction/Art/Architecture classes can look after design, and either specific classes or any students could handle the creation of the space.
An outdoor classroom could provide a lower cost opportunity. This could be constructed in any open space in the school yard.
An indoor structure would likely come with a higher cost, but could provide more additional use with protection from the elements.