In my opinion, if your algorithm is that solid and unique, that's your real selling point.

This whole "you can't control the player" is a bad idea, it doesn't drive the usual gamer and you're going to find that maybe it's exciting for people to watch their creature fight the first time but there's no repeat value in that (watching the same moves over and over and over again just isn't exciting).

The perfect blend of your idea and the wishes of the masses is to have your 'Cornelius' algorithm analyze the drawing then return a skill set. So it gives the player 6 movies + 10 combo moves based on their drawings attributes. You get a combination of the "my ninja vs. your ninja" as well as the ability to actually influence the outcome and promote replay value.