After giving it a try, I think It would be a cool addition to the steam store. The reason I picked the demo up is because I freaking love Jet Set Radio/JSRF and I saw a post on the let's play subreddit.
Yes I would play the full game, Depending on price and my enjoyment!
I know this is just a prototype so I don't have much to say that I think you'll already be planning on doing like different music going on and such XD