Luke,  I have a couple comments for your hybrid player piano project.
How about making a sketch of the interface between the pneumatic action
in the player to the keys of the electronic piano so we can see what
you're doing?

A friend of mine did the same thing many years ago but he just inverted
the keyboard, like you originally mentioned, because he didn't care
about the physical arrangement.  You're certainly right that watching
the keys move is an important part of the performance.

Also, I wonder if you realize that you have made a rather useful analog
to digital converter -- also known as a piano roll reader.  If your
keyboard has a MIDI OUT port, you can save the file, just like the
more elaborate roll scanners do.  It won't be quite as precise as they
are, but for casual listening it would be just fine.

Regards,
Craig Smith
Upstate New York