Plyron is an exterior grade plywood that has a hardboard surface. You can also buy it in a tempered condition. Despite it's costs it works well for stage decks, particularly since you can lay one floor. One theatre I worked at made its own with a sheet of plywood (I think they used 3/4" cdx) glued between 2 (one on top and one on bottom) sheets of masonite.
Load span tables are available at:
Another Simpson Product is Skidgaurd. While I have not used it, I would be curious about the theatrical use of the product, particularly on rakes, or where masonites slippery surface is a problem. The surface would not have the same finished edge of course, but the safety factor would make it a worthwhile material to test. More information on that can be found at:
Another nontheatrical sheet product is Arborite. It has a high strength to weight ratio, and has good electrical and mechanical properties. A PDF describing its qualities is available at: