Haha yes

My dad's conspiracy theory is that a week or so after becoming president, Biden steps down and let's Harris take over.
(we're not Americans so we have no stake in this)

Many would not have a problem with this. Perhaps even welcome it.

I wouldn't be mad. And I've heard this theory too.

If Biden's goal really is to unify the people, I think he should wait at least two years before going for the switcheroo, anything earlier and republican voters will probably cry foul over that people didn't vote for Harris.
But that's just my two cents as an outsider.