This is a no-brainer!  As far as the odd request in the past thread,
that someone needs to dance on top of a player piano for a show, the
solution is easy.

Prepare a replacement top for the piano.  'Veneer' it with wood-grained
kitchen counter-top material (Formica) as close to the original top as
possible.  After the show is over, reinstall the original top.  No harm
done!

But, if the front of the piano faces the stage, make the top oversize,
by about 2 to 3 feet toward the back, and run some supports from the
back of it, all the way down to the floor.  This will keep the piano
from tipping over.

The only "light" player piano I have seen was a few years ago.  It was
a pneumatic player, but the piano was actually a electronic keyboard.
Looked like a studio upright.  I don't know who built the thing, but
it only stayed around a year or so.

Here is what this show really needs to fill the requirements: a gutted
upright outfitted with the QRS "Presto Digitation".  I think they also
sell an attachment for this that animates the keys while receiving MIDI
signals.  Without the plate, the piano would be light, and would be
easy to amplify; it looks "old", and can be played by hand.  (To make
it even lighter, remove the back and install a piece of plywood.)

If a "scrolling roll" is desired, an old player piano case and a spool
box with a short piece of player roll around the spools in a loop,
powered with a electric motor, should complete the illusion.

Cheers

Andy Taylor
Tempola Music Rolls