At worst he’ll make shanks a snape or itachi like character, no more.
Not every strong character has to be a mastermind and turn evil.
Shanks' role from day 1 has been similar to Itachi or of a big brother/teacher. Many readers tend to like this type of characters.
Your view of Shanks can be different from others. As a Shanks fan, I dont care about him being greater or weaker than Mihawk.
My view is that he is content with his fate, he is not fightig against it just like Roger gave up after finding out he is not the one.
People associate Blackbeard with Luffy, but if you look at it Blackbeard and Shanks also present two constrasting approaches.
Why? Whitebeard said to BB that "You are not the one", but BB is still going against his fate and trying to be that "one". While Shanks just accepted his fate. I dont know why so many readers ignore this point when Shanks has been shown to chase BB for almost 2 decades now.
I think there is lack of character analysis regarding Shanks, less threads, less explanations, and no or low effort from Shanks fans to convey how they actually percieve his character. Or at least, how Oda wants it to show to his readers.