The pushback comes from people who think there will be two separate big arcs for Blackbeard and the World Government. Heck some were even suggesting an Elbaf arc where Big Mom comes back. Its pretty clear to me that Oda will pack all the fights into a big final war that makes "Marineford look cute".
Yep.
Look at Zoro vs Mihawk for example.
A bunch of people try to think how Mihawk will fight against the Alliance in the Final War so that Zoro could fight him.
This doesn't matter at all, Mihawk won't really give a shit about this fight between powers. He only cares to kill his own boredom.
Just re-reading Baratie it's clear, Mihawk wasn't against the Straw Hats or on the side of Krieg, he just wanted to kill his boredom and found a fight with Zoro.
I think Mihawk can start fighting alongside the pirates of the Alliance, as most Warlords will, and then when he meets Zoro in the middle of the battlefield, they will stop and face each other.
And you will see a bunch of pirates and marines stop to watch this legendary duel, just like they did in Baratie.
There doesn't need to be all this reasoning behind Mihawk being on the other side or anything like that.