I'd like to see a few more structure permission options available...
1) Friends Only - Once selected and the button to save changes clicked a new window would popup to add player names to with the option to drag and drop names from your Player List available. Then just do a final save and only those players on that list can access those particular structures.
2) Guild Rank Only - Once selected and the button to save changes clicked a new window would popup to add guild ranks to it with an option to drag and drop ranks from the Structure tab of the Guild window. Then just do a final save and only those players within those ranks on the list can access those particular structures.
3) Guild & Friends Only - Once selected and the button to save changes clicked all guild members would be allowed and a new window would popup to add player names to with the option to drag and drop names from your Player List available. Then just do a final save and only guild members and players on that list can access those particular structures.
4) Account Only - This should actually already be in and be a passive thing but since it isn't then make it a structure option. Selecting this permission would instantly allow all characters on a single account access to that structure.