Yes, if needed it could be resin filled in the riser section maybe?.

Its a crap-shoot i guess - was thinking 12mm plate, welded into box style weldments - big one for the swivel connector and riser section finishing in a vertical plate for the Z slide carriages. Then a box style extender starting with the Z rails and then motor/spindle cartridge.

I guess it will need a medium/high pre-load rail set to ensure no slack in Z axes, good quality stuff and a decent screw to lift it all, maybe counterbalanced as well??