Don't forget about the privacy cost associated with the canvas. If this ever becomes widespread, we will have many many sites extract browser fingerprinting information from the canvas. It would then move the game one more step towards dystopia, where we have to analyze and block certain ways of code interacting with the canvas and it might even prove impossible. And then incapable web devs will offer you no solution but canvas buttons for the login to your bank account. No, I don't think this is the way forward.