I don't know yet. I'm trying to use my writer's brain on the fly here. This is just what I would do if I was Oda at this moment.
If it's like he left a journal or something at Lodestar and that's why they have to go, sure. But him being a ghost or living in the DF? No thank you.
Oh no, Imu's powers bordering on outright magic is bad enough, we don't need outright supernatural stuff.