If you have not seen this already its worth looking at and just wondered how we could do this for the Taz !
https://www.kickstarter.com/projects/1661525705/z-unlimited-add-on-for-ultimaker
The taller a print gets, the more likely it will be knocked out of allignment or off the bed entirely. I guess if you had some secondary support clamping mechanism you could do that, but it would likely not be all that precise. I think it would be far easier to print sections with keyed allignment posts and then glue them together to form a large assembly than that particular approach.
Probably unlikely… The Ultimaker has a stationary bed. Even with a stationary bed, there are a lot of print characteristics which need to be tweaked.
Increasing the Z-height of the Lulzbot and welding parts together would probably be better. It would really suck, if you got 4’ into a project and it delaminates or decides to topple over.