A MAP EDITOR IS POSSIBLE. To make a similar Map Editor like MTA is possible. It just needs shitloads of Object hashes to be added to a table, and might a proper GUI interface. I doub it will be fastly done in a proper way, but doing it with some decent script is possible, yes. Also IV:MP does allow setPlayerInterior and maybe soon the better version setPlayerVirtualWorld. Therefore private Interiors releated to a property would become possible, as long someone finds time to script that tool. I doub we have time during the soon starting RS2 development.
So it is just a question of time when it will be possible or more, when it is ready. But today we won't have time for it.