Vista would've been the perfect timeskip teacher.
Just create a scenario where Shiryu clapped Vista during the Payback war (have it be right after Marineford) with Vista retiring back to his home island and Kuma sends Zoro there beforehand.
Zoro begs Vista for Haki training, knowing that Zoro's a friend of Ace's brother, Vista senses WSS potential within him and agrees. Zoro surpasses him by the end of timeskip then goes on to avenge him by clapping Shiryu EoS.
On the other hand, Mihawk never met Zoro or Perona during the timeskip, so he would've been less kind with a more ruthless, villainous role during the rest of the story as Zoro's clear, unquestionable final enemy. You might as well throw in Mihawk killing someone close to Zoro to fuel the rivalry.
Give us evil Mihawk ffs.