The logic that Shanks solely exists to be a hypetool for Teach has to be one of the most ridiculous claims Ive heard in this manga. He has existed nearly 140 chapters before Blackbeard was even referenced as a concept in the story. Blackbeard himself isnt ever shown in any early drafts or Romance dawn iterations. But you know who was? Boa Hancock and other shichibukai. Garp (who is not nearly as important to the story as Shanks or Blackbeard). Most of the strawhats. So to claim that Oda's ultimate goal for Shanks is a Blackbeard offscreen or hypetool (right after he just used Law and Kid for that) is frankly ridiculous.
There is nothing, narratively, that supports the idea. People use weird shit like Shanks is the "Dumbledore" or "Jiraiya" of One Piece when he quite literally is not Luffy's mentor whatsoever (thats Rayleigh and even earlier in his life after Shanks left, Garp) and more a manipulator of events.
But what do I know.