WTF are those symbols and letters though?
I have no elements to say how suited this could be for actual performance (now idea how solid it feels, how well it responds to velocity, etc) but I have few doubts this could be a great composition tool... thinking of piano reductions on steroids and easy transposition.
If you really manage to keep this at around $350 (as you said half of £530) and properly marketed, it could be very interesting