Crazy? No. The timing and optics would be wrong since Sanders wouldn't help Harris' campaign play to its advantages. Finding younger candidates with consistent and (hopefully) progressive records, who aren't currently targets for the Right, and who hold little political baggage, is a better play.
By the same reasoning I think Newsom and Buttigieg aren't good picks even though they'd do well in the role. The new Dem Pres campaign should make sure the Right's propagandists have to work hard at effective attack ads. Running any Left-Wing Face misses this initiative.
For context: I'm still bitter about Bernie being pushed out of previous Presidential campaign runs, still think he was the best choice both times, and know he'd make a great VP.
Primary goal for the DNC has to be to distance themselves as much as possible from the age issue. I'm not saying it will be someone young, we're not getting someone like under 45ish, but priority has to be on getting someone who at least comes across as relatively youthful comparatively.
I mean, if people think kamala is very progressive then yes. Age and policy wise. The VP should net you votes you might not otherwise get. A Midwestern pick or similar would probably do well.