Yes indeed, I was simply trying to work with what was there already.
As I did after all say- "or a single motor".
If I were designing a mechanism such as this from scratch I would go that route without doubt (but also would fit a 24V PSU, line-fed bed heater, graphic display, decent end stop switches, and on and on).
I have worked with "robots" that have had up to 20'x60'x12' (yes, feet) motions such as industrial laser cutters and CNC machining centers.
They invariably used single motors for each axis.
They had single or dual lead screws for shorter axes and typically (but not always) chains, belts or bands for longer ones.
Where they did use dual lead screws (or chains, belts, bands, etc) on an axis they were synchronized to that single axis motor by means of precision zero-backlash timing belts or chains, or in certain applications- jack shafts.
Of course these tended to cost 100x-2000x the price of the FT-5 and so their designers could afford to do such things.
However. because dual axis drive motors seem to be endemic in the 3D printer world, and do in fact work (though not without headaches), I would still characterize synchronizing them via a belt or chain as an "upgrade".
Unless of course a single motor was used to start with, in which case a timing belt is the most reasonable option for driving multiple lead screws from it and there are many printers that do just that.