Save (or lock) realms through tiered portal

Would be great in future development where higher tiered portal would permit you to "save" a particular realm. My take on it would be to have said portal grant the player a specific address card for it (much like the respite address card) When use on a "normal" portal this card would permit travel to that portal. Only one instance of a these specific portal would be permitted at once. Player would have to physically travel to the portal realm in order to deconstruct it (thus preventing the accidental deleting by duplication). In online mode, owning player would be able to create address card to give to other players. This would allow to save farming realms while permitting the resetting of said realm for thew purpose of strip mining it, having it tiered would allow to have more than the one special portal and should required special and rare materials to construct.