a big question is:
do we need fast travel?
i played daoc back when and they only had horse taxies which you could jump off of. now cities are created in fractured so it could be a challenge to add them.
there's also the use of alts to get things done in areas your main isn't in.
to counter that, i love having the option of cities (of a certain size) that can build a portal element into the ground (or arch) and let the players activate them. I've watched Critical Role and the use of a daily portal is pretty convenient but having that be unlocked by the player. Maybe it starts by learning how to teleport x yards in a direction. that spell could be the foundation to learn how to teleport further distances.
i don't like the idea of just giving the players a way to teleport between cities/house. to me they need to earn it both with the city/house and the knowledge system.