How do you think Mihawk will be relevant in the future then?
What will be his goal? If he isn't searching One Piece with a crew, he can't have a bigger role.
Mihawk fighting Zolo on a random island when crew doing nothing = no tension, no excitement, we know Zolo needs to win, if Zolo loses, no big deal, their primary goal is finding One Piece.
Mihawk fighting Zolo while Luffy fights Blackbeard or Shanks = Mihawk serving to Shanks or Blackbeard, Oda wouldn't do this.