Would it be possible to add a way to knock on locked doors? It would make IC sense for people outside to have a way to get the attention of people inside a building, and the other way around.
An alternate suggestion is a special emote that you can do to doors. Something like the whisper? But what happens is that it shows up in the present room, and the next room. It lets you knock or yell/shout emote at the door itself.