There is always the possibility to bring untradeable crafted gears.
All what Yoshida need to do to make it possible would be bringing ingame untradeable mats from dungeons and a feature where other players can craft for you without giving them the mats for it (like the materia request feature).
This way dungeon raiders still get their gear from dungeons (even if only as a mat at first), crafters can craft for endlevel players and RMT are not involved