...Based on this, I'm not really sure that Luffy is actually defeated or it's going to be some sort of Fakeout.
But anyway, I think it's worth remembering, now that Luffy and Loki(?) are seemingly out of the picture, there is literally nothing stopping Imu from using Domni reversi on every single character on Elbaf(but chopper, I guess?). There's literally zero restrictions on the power as far as we know. Imu just hasn't been using it since he arrived in person,because....?
Only Oda knows.