I have thought of doing this myself. I thought it would probably work especially well for me since I have an under the floor single master cylinder. You could probably use a clutch slave cylinder on the other side of your booster too so that would probably be pretty easy. The thing I didn't like about it is it introduces a third failure point. The other thing I wasn't sure of was how to bleed the thing if the slave was higher than the master, which in my case it almost had to be.