It’s interesting as an intellectual exercise; But IMO the US Congress and more particularly the people do not have 1/500th of the attention span to manage such a complex unwinding process.
Suppose for the sake of brain twist we get to the kind of point you image in let’s say October-December. In one case, the elections have not yet been held, in the other, they have, and HRC wins. 0bama is discovered to have committed deep treason, so serious that even Dems look like they’ll vote to impeach him. What then?
He resigns, Biden steps in, pardons HRC, same result. We are hosed.
Ah, but wasn't it also the Senate (including Senator Biden) who certified the Electoral College's vote and thus perpetrated that fraud? IOW, wouldn't he in effect be pardoning crimes he was personally involved in?
Nemo iudex in causa sua
(No-one should be a judge in his own cause.)