This first is that it's another empty, reprehensible cry from Republicans designed solely to distract and undercut a sense of authority -- which is one of the core tenets of fascism -- and that, of course, he shouldn't be required to testify because it sets an utterly awful precedent.
The other is that Adam Schiff would be an incredible witness, soft-spoken, on point with all his facts, and full of restrained anger with a complete sense of making clear the case against Trump. And I would dearly love to see him on the witness stand. The only semi-serious question that Republicans could ask him would be about him knowing the identity of the whistleblower. He would say, under oath, what he's said publicly -- that he doesn't know, and after that point Republicans would have pretty much nothing to ask him. But Democrats would, and they would provide an open floor for him to shred Trump.
As I said, though, it sets a terrible precedent, and I default to my initial feeling. That said, there is only condition on which I could see supporting him testifying -- and that's for him to say, "For me to testify, I believe it is critical that fairness be observed and, as such, that the committee leaders of both parities agree to testify. And so, if I testify, so much the ranking member Devin Nunes."
There may be next to nothing that Rep. Schiff could be seriously questioned about, but there is an abundance that Rep. Nunes (R-C) could. And at its heart are the news stories of him traveling to Ukraine with Lev Parnas, the associate of Trump's lawyer Rudy Giuliani. There is so much that Democrats would love to ask him about that, under oath. And that aside, the image of Nunes flailing in red-faced fury, as his does, in contest to the mature calm of Adam Schiff would be palpable. Even if Nunes pleaded the Fifth to all questions about his activities, indeed almost because of that, his credibility as leader of the committee Republicans would be shot.
That won't happen. But I'd still love to hear the suggestion made, if only for the image of Republicans scurrying to hide as they er-hem and harrumph down the hallway...