WezV: The distortion things you can buy usually have to use the pot suppled, as they have a circuit board attatched to it...
However, using the concentric so that the top is tone and the bottom is volume (or vice versa) and then the other hole can have the distortion pot put in it - that's the only way I can think of to work it, or what Phil said, so that you just click a switch and it gets a "drop" in tone - but the concentric pot thing leaves you with full variation of the tone control :)