So this idea might have already come up or considered but I wanna post it anyway in case it wasn't.
The simple idea is to utilize the house/cave 'zone' system, to create the illusion of an under ground bridge. Basically a claim owner would have to build two separate buildings to form the bridge and you could walk into one, (an entrance building) then walk out the other (exit building) using the zone system. Figured, having it one way would be simpler to implement but could be wrong.
I was thinking a zone with two exits that way each bridge building would link to a specific spot within the zone. Another idea might be like the hideout where you talk to an NPC that spits you back out on the other side.
The hardest part would probably be being able to link the two buildings so the game knows where to put your character.
The buildings need to have a range cap so people can't exploit them for teleports, and need to stay within the same claim.
Possibly using tp energy as well?
Probably should generate a small amount of hex for the claim owner per use that would be capped daily.
The buildings could even be tiered to allow only person/cart/wagon/etc through.
If the system is functional it could also be used as a canal for boats, or as stairs to get into mountain claims.
Any other ideas or considerations?