You can read my sig link to see how I feel about this. Clearly you don't understand my point of view and that's fine. But it's not "highly unlikely" if you've been following the trail Oda has been leaving about the character.
Never even stated Shanks is evil. Antagonist does not equate an Evil Villain. That's better reserved for Blackbeard or Im or Akainu. And that's not at all what im talking about.
If Mihawk were to ally with Shanks, i would assume it would be because Mihawk knows Shanks and Luffy are on a collision course, thereby being the highest chance for Zoro and him to encounter each other.
Think about this, what other faction is there a place for Mihawk? He 100% will not ally with Blackbeard, whom already has a Swordsman as his 2nd command. He just got booted from the Shichibukai, so the Marines and WG are also out of the question. What is left, but the only rival he has?
And if the other option is "Zoro and Mihawk will randomly fight somewhere in the EoS" than that goes heavily against how Oda even sets up faction based fights in this series. Fights aren't random. They are always tied to the crew vs another faction. Mihawk won't be some special irrelevant fight outside of the main plot, he WILL be part of the main plot