Not a bad idea, I try it, but no result
@Pode said "this plugin doesn't draw to canvas. I'm using a <div> on top of C2's canvas"
I see the html source code, in fact, the iframe is after the canvas construct:
<div id="c2canvasdiv" ... </div>
<iframe src="... </iframe>
Maybe it's because "Fullscreen" function works on c2canvasid, so when we active "Fullscreen request" the iframe is out ?