I've been using a handy shader in Clickteam Fusion that uses an object's alpha value to dither it instead of give it semi-transparency. I don't need the shader to replace semi-transparency necessarily. It only needs to dither an object based on a value.
I'm not sure if there's a way to convert Fusion shaders to C2 ones, but I can send the code for it. Willing to pay for this.
Email me or tweet me JayTholen or just reply if you can do it.
Should look like this if you decrease the value gradually: