gradbert: cool. I actually did something similar (see: Arduino Starter Kit kaufen [verschiedene Ausführungen]), but you've got some nice improvements. I like the name Printable better than Print, which is what I used. Also, did you get this to work on the Arduino? I had trouble getting virtual functions to compile, so I hacked together my own version.
I did get it working. In the zip file is an example program that will compile, download, and display on an lcd. The only thing that was really giving me a problem was that the build doesn't seem to be very happy with a library including another library, so in my sketch I have to explicitly include <Printable.h>.
Now because the pin assignments are local to the instance of the object, I should be able to hook up two lcd displays at once. If I have some time this week, I will make a second lcd cable and try it.