I want to do this, but I haven't managed to dig up any information on a fast variable-radius gaussian blur algorithm. If you open the .fx files in the Effects folder for the blurs, you'll see they're hard coded with the blur values for 13 pixel blur. If you can find any more info on this, I'd gladly have a shot at variable blurs!
Well, I'm an artist, not a coder.
I just assumed that "13" would be easy to replace with a "INSERT VALUE HERE". Forgive my ignorance.