If POTUS testifies it should be last after all the Dem scumbags. That would really be using his office for Political Advantage. Bully Pulpit!
“I want Hunter Biden, Joe Biden, Barack Obama, Adam Schiff to testify”
I can maybe see Trump agreeing in a deal where this batch also agrees but it would still have to a very limited scope of questioning centered around whatever specific charges they bring. And “Orange Man Bad” is not a specific charge either...even though that seems to be the centerpiece of their argument.