kompressor, just an idea, but when converting bedroom saves and stuff to slate saves, if you get the lowest point of the build (the baseplate) and drop that to Z-Level 0, anything constructed on a single plane (like the floor of the bedroom) will port over to this new construct map perfectly. There'll be some floaters if anything is built on the dresser and floor at the same time, but with some advanced algorithms you can drop all non-contiguous baseplates to Z-Level 0 as well.
In other words, stop freaking out over saves. It's totally possible to bring stuff over to a slate map.
(Subliminal Message: Please make dedicated saving a possibility this update. <3? )
I would've personally just loaded my previous saves over into a slate world. (Assuming I can do that, for I don't know what happens to the folders that saves are in if their relevant map is removed)
And from there, I'd have used a duplicator to bring down all the floating pieces and put them down on the floor of Slate.
I obviously wouldn't be able to re-use them like I had them intended, but it'd be interesting and nice to have all my hard-work and favourite parts available for me to re-use or view when I like. (I like to get nostalgic over my old builds from time to time. :3)
I would even consider gathering all my old terrain/interior-map based saves, taking the best parts of them and putting them all together in a large museum build dedicated to my old works.
That might sound silly to anyone else, but I've got a lot of memory from building and roleplaying in builds, so I'd love to do something like that.
And I could give people tours. :3
Or just show off what I've done in the past.