You might also be interested in Picotron[1], made by the same guy who made Pico8. It's basically a desktop OS with the same basic design as Pico8 but with slightly looser restrictions. I've never really tried it, only looked at his gifs once a long time ago, but I think he and I had the same basic idea: make a platform that you could make pico8 in. We just went different routes.