With all due respect, you are mistaken in several points. There’s no such thing as a continuous “record” among related proceedings - the trial testimony of the witnesses we just heard is not any more or less admissible in any future proceeding. It will be subject to the same analysis as to its admissibility as any other proposed evidence.

There are much, much easier ways to secure statements from witnesses than to hold an entire trial - the entire idea does not make sense to any lawyer.