President Trump should make it VERY clear that he will fight all witnesses that may be hostile to him IN COURT. How will the Senate like doing NOTHING but the impeachment trial for the next few months with nothing but favorable witnesses sent up by President?
The problem with that thought is that you're counting on the Senate to allow Trump any witnesses. I think that there would be enough rinos led my Mitt voting to disallow Trump any witnesses. Mitt will take the position that Trump called witnesses "aren't relevant".