Quick question, perhaps: what's the maximum computing power, especially RAM, you're thinking of offering?
If it's just microcontrollers, my interest in somewhat limited. Something I reasonably put a Lisp on (code as data wants RAM, even if a lot can live on flash) ... well, looking at Wikipedia's list of Arduino CPUs, 96KiB is a very qualified maybe, 64MiB is a lot more like it.
Disclosure - I wrote the post.