Luke Myers asks whether this has been done before [160514 MMDigest].
Well, sort of!  Last year members of the Musical Box Society of Great
Britain visited Stowe Maries Great War aerodrome in Essex, UK, where
they use a "push-up" piano player to play an electronic keyboard.
Also, some years ago, a member of MBSGB demonstrated his rare 36-note
disc operated piano player with an electronic keyboard.

Using a push-up piano player is the most straightforward solution
to Luke's problem, although you do need an 88-note keyboard (65-note
minimum) for it to work first time on an unmodified push-up.  Push-ups
seem to be quite cheap or even free these days so this should be an
inexpensive option and easier to cope with than a full player piano.

Using an orphaned player action presents a number of problems.  First
you need a framework to support the action, spool box, roll motor,
tracking mechanism, and the pumping mechanism.  Then you have to figure
out and build a means of reversing the output from the note pneumatics
which usually push or pull upwards, since you need a downwards action
to operate the keyboard.  Not a simple task, I suspect, but good luck
to Luke if he decides to take on such a project.

Best wishes for the UK,
John Farmer - MBSGB