An intriguing theory I heard on Michael Smerconish's show - If Republicans "trade" witnesses, like allowing Bolton in trade for allowing Hunter Biden, it could be a net win for Democrats, because Hunter Biden could be a great witness.
Its only a 'win' in the same way as paying the ransom on a kidnapping is a 'win' for the victim.
There is no reason for Hunter biden to be called. He was not privy to Trump's phone call, nor was he involved in the cover up. Furthermore, there is no actual evidence that he did anything wrong at all. There is no legal or moral argument for Biden to be called at all.
Even if Biden turns out to be a 'good' witness, and doesn't somehow make the democrats look bad, he should not be within a 100 miles of the impeachment proceedings.
Of course if I were him and he did get called, I would take any question that was asked and turn it back on the republicans and the GOP. Answer all the questions with irrelevant statements.
Republican: "Do you think you were qualified to work for Burisma"
Biden: "I am more qualified than Kushner is to work for the white house... after all, my dad didn't go to jail"
Republican: "Why were you paid a lot?"
Biden: "I got paid a lot because I wasn't a hypocrite like Ken Starr"
Republican: "Did you commit criminal acts?"
Biden: "Why am I being questioned about criminality by the republicans, a group that includes 'gym' Jordan, who ignored crime that happened when he worked for Ohio state?"