I think that the Biden problem resolution has already been decided.
There is consensus among the top Democrats, Obama, Pelosi, Hillary, that is indicated by their support. Absent a plan known to the consensus there is no reason to publically endorse Biden in advance of the convention.
So, what then is the plan?
1. They have conceded the election and are protecting the party at the convention
2. They are planning a dirty trick. They are going to steal the election at the gathering of the electors in the House of Representatives
3. Some other dirty trick inviting a civil war.
Never forget the power of the liberal media. When Obama was running, they covered up all his negatives, pushed him across the finish line. Today, the liberal media is all in for Biden and will continue the Hate Trump Train.
My biggest fear would fall under your number 3... assassination of BOTH the President and VP. They manage to take them both out, Nanzi Peelousy becomes CinC.
I have a feeling that when the President wins in November, the forces of evil will fall to their last desperate card to play. They could use a couple of brainwashed idiots whom they convince that the world is dead if Trump and Pence continue to live. Hell, there are idiots out there RIGHT NOW who think that.