This one is new to me:
An even more radical idea has been put forward by Swedish diplomat Mathias Mossberg and UC-Irvine professor Mark LeVine. They do not believe giving settlers Palestinian passports would solve anything. The two propose creating overlapping states between the Jordan River and Mediterranean Sea, delinking the concept of state sovereignty from a specific territory. There would be an Israel and a Palestine, but rather than divide the land, the two states would be superimposed on top of one another. The plan would permit individuals to live where they wish and choose their political allegiance. This, they argue, would resolve the seemingly intractable questions of how to divide the holy city of Jerusalem and whether to allow Palestinian refugees “the right of return” to their old communities.
This doesn't seem practicable to me (no good mechanism for dispute resolution), but maybe in some other geopolitical setting it could be made to work,