SNL has their own writers and creative staff. If Weird Al were to be a guest host, he would need to play by their rules and perform their material. And SNL's comedy style isn't really congruent with what Weird Al does.
I wouldn't want to see him on SNL unless he and his people got to work with the creative staff from top to bottom.
They do cater to the host. Bad Bunny got the first Spanish sketch, Adam Driver always gets stuff he can play hilariously serious. They would absolutely figure out sketches for Weird Al. I know people love to shit on SNL but they have a lot of extremely talented people.
... I mean I think he's aware of how it works. Weird Al, given his track record with respecting other people's work even above what he is required to do, doesn't seem like the type to ask to be a part of it and then demand it to be done his way.
I think they could make something work. SNL has its own style, but they tend to adore when they have comedic hosts who will play the goofy roles. Weird Al seems like a great fit... Musical numbers, collaborations with Please Don't Destroy... I think it has big potential.