I thought some of ya might find this interesting. It's a primitive tremelo using interchangable discs. Certainly no hearty enough for gigging, but could be fun in the studio.

I made one...it was a fun little project. Fine for home use...not even close to being practical on stage. 

I do build a pretty sweet tremolo myself though.... check it ;)

http://elreyfx.com/html/chicago.html

very cool. I think if you put a clear enclosure over the disc and made the switch into a footswitch youd make this a lot more practical.