3d printer project

Hi All,

After looking at how my lexmark works I'm thinking on how to make
the mechanics to make it print.
here is how I would do it.
set it to move the print head along the powder to print.
when it's done, send a printer busy signal to computer this will
pause the printer.
Build a step motor drive + a microprocessor that will move the print
head assembly backwards to the build piston with a fresh layer to be
deposit.
move the head assembly to the printing start position( this would
deposit the new layer on top of the just printed layer.)
Releasy the busy signal and let the printer print the next layer.

This way I should not need to make the motors on the printer itself
reverse direction, nor should i make any major changes to the
printer electronics.

What you Guys think ?