Didn't Work Well in 1967
Unless we are talking about a Korean situation, I think the UN should stay out.
Maybe we could build on Sharon's idea and simply put up a vigorous embargo and blockaed on everything coming and going, and freeze all assets of all parties until a single entitiy is in place to speak for all based on equality of property rights, equality of access to the entire territory and equality of all other civil rights for all residents of the area.
Then we could take down the walls and let them rejoin civilization.
Ed