Floppyrat, I had the same idea some time ago, explained in this (somewhat hi-jacked) thread:
http://www.subsim.com/radioroom/showthread.php?t=194563
I finally ordered an Arduino set, which I haven't had the time to look at, and an Enigma-E set (from Bletchley Park) which I also haven't had the time to build.
But it sounds awesome, no-one can disagree on that
