To clarify, I don't think
@Cinera is jumping any bandwagon here.
Personally, I consider this reincarnation BS to be stupid, but Luffy being Joyboy does have a narrative purpose (lousy tho it is) in that Joyboy has unfinished business with the Ancient Weapons, the One Piece, Void Century, Toki, and the Will of D, which have been hinted and mentioned by Oda all throughout the series.
The thing is: what narrative purpose relates to Zoro actually being Ryuma? None of the aforementioned plotlines, that's for sure. Heck, not even Kaido has anything to do with Ryuma (since they never even met) and I'm a staunch supporter of ZKK, so we know it's not necessary for Zoro to be Ryuma for ZKK to happen.
And as previously mentioned, unless Oda is going to pretend that Thriller Bark is no longer canon, then Ryuma was literally interacting with himself without noticing it at all (which is senseless, even for One Piece standards). There is also the whole Shusui debacle to consider.
Zoro being a figurative second coming of Ryuma is inevitable. Zoro being a literal second coming of Ryuma is mind-numbing.