This one's a stretch...

It certainly clears up the 3rd-axis clearance-issue, but:

* may be quite a bit more difficult to run the cables/pulleys

* might not be stable-enough for merely two casters on the 'bed', should I use four?

(otoh, now that I think about it, part of the niceness-discovered with the pulley/lego system was that the cables, when positioned and tensioned well, actually add to overall stability quite-nicely)

* appears to use quite a bit more material for the same travel-distances...

* more difficult to add support left-to-right... may need longer bed-casters...

* can't add front-to-back support in the front

* kinda bulky/ugly...

Nicities:

* lots of vertical clearance for potential 3D-stuff....

* easier to make the Y/Z carriages larger, to mount larger things (dremmel-tool?)

* The Z-axis should be *quite a bit* stronger

* (maybe the Y, as well?)

* The Z-axis carriage and associated cable-tensions might actually add some stability

things to think about...