Ballot access is for the party, and literally NOT the candidate. Voters vote for and choose presidential electors. The candidate names appear only as a crutch to facilitate completing a ballot.
And even after the general election, the party can change who the electors will name, in the ballots they send to Congress. This would be done if a candidate became unavailable.
It will come to a plea deal. Clinton steps down from the campaign and serves no time.
I bet it goes down like this. Hillary goes to the convention and picks Joe Biden as her vice president. The convention elects the team, shutting out Bernie Sanders. After the convention, Clinton steps aside and Joe Biden goes to the top of the ticket and picks another vice president (ala George McGovern, Eagleton and Shriver).
It won’t work for them, but it’s the only straw the dims have to grasp.