Still not sure about Dragon.
Dragon has more the "he fights Imu, but Imu takes him down as a hypetool, revos act more like a support force".
My bet would be
Luffy vs Imu.
And, for the remaining 4 Gorosei (saturn loses here on egghead):
Zoro
Sanji
Jimbe
Either Law or Usopp (this here is more of a wishful thinking than anything xD, but Law is a real contender).
Imo, Dragon is basically the Wyper to Im's Enel.
And just like how Wyper (strongest fighter from Shandia) beat Shura or how Kyros (strongest fighter from Dressrosa) beat Diamante or how Inuarashi (strongest fighter from Zou/strongest scabbard from Wano) beat Jack... Dragon will play that role at the Final War imo.
I also think Dragon will face Imu after that, just like Wyper faced Enel.
Dragon probably has one secret way to take out Imu, just like Wyper tried to take out Enel.
But Dragon will fail and get neg diff'd, just like what happened to Wyper.
Before God's Natural Enemy Luffy saves the day.