@Pode: Sounds very good.
There is one thing I do not understand. When I look at the demo of the "Extract Sprite" behavior the extracted base64-string with chrome and webgl seems to be wrong. But - when I use the behavior in my plugin-demo the sprite extract with your plugin is the only thing that works on chrome with webGL. I suppose that the blank-images bug has a painting origin.
I've built a similar behavior like yours for extracting the base64 of the C2-cangs. It works perfect on FF.. very great but it also fails on Chrome - useless.