Interesting construction for sure, I like the idea of simple controls, but why stop with only 2 oscillators available for the ring mod. It would be just as simple to add an input allowing for processing of external sources like guitar or other instruments. Anyways its not my call on this one. For more info on ring mods and how they work check out this paper.
http://www.du.edu/~etuttle/electron/elect61.htm