Sadly the closest method is shell Free Companys at the moment. Although even that has limits such as the inability to put treasure maps in the company chest. Also can't mail stuff to yourself unless its through a 2nd account which can be used for treasure map storage.

For the shell FC, you basically need a friend to setup an FC petition and you sign up with each of your characters into the FC. Then the FC leader relinquishes control of the FC to whichever character of yours is your primary.