I like the idea of calling witnesses but I'm afraid that Creepy Joe, Hunter, the whistleblower, et all will only plead the 5th and result in a huge waste of time. Particularly when you consider how much they'll fight it to even begin with.
IF witnesses are a part of The Plan then Bolton has to be a land mine, disguised as bait for Schiff and the Ds. He's the only one who would necessarily need to plead the 5th (at least on the surface) and could spill the beans on everything going on behind the scenes.
Just a thought. Welcome back, Q.