I don't know how simple it would be to add. To me it looks not so simple with my imperfect understanding of how C2's renderer works.
However that's not my my point. My point is it is this could be done in a plugin currently, if you're willing to use webgl directly. Most plugins just use C2's provided drawing functions within the drawgl() function, but you can use any webgl in there as long as you:
A. finish C2's current render batches at the start of the function.
B. At the end set any webgl states you changed back to what they were at the start. There are some that don't need to restore, it just depends on what the renderer expects to stay the same.
As a cursory exploration into this I did some custom webgl in this plugin:
Basically it draws one large 2d mesh instead of multiple quads. In a similar way you can use your own fragment and pixel shaders and give them any parameters you'd like. This is where you'll need a good webgl tutorial as C2's way of using effects wouldn't be used.