I have always been curious but unsure whether it woule be possible in Rust. 
However, would it be possible to create a plugin that would allow the saving of an area as a home (like NTeleportation) without the need of a foundation?
My basic premise behind this is to use it for water bases and not having to worry about drowning because they are spawning on a foundation in water. If they built a tower from the bottom of the water up they could spawn on the top.
Again, not sure if this is possible

I think in some of the recent builds of NTeleportation they allow this.