I suggest the new structure made of Reinforced Deepslate in the Ancient Cities that look somewhat like a portal become a new feature for teleportation between two points.
Either through some form of beacon-esque ritual of activation, or perhaps the use of a new rare loot item, two of these structures could become linked together and allow transport between two points in the overworld. (Like setting a frequency and tuning them both into it).
eg. right clicking an item on frame one saves coordinates, and then right clicking on frame two makes the link. Then perform X ritual to activate portal.
Keeping the current properties of being unobtainable by breaking and only movable by piston would make this one of the most highly prized blocks in the game