This weekend the previous president was whining that he wants equal time to give his side of the story. The Committee would relish the chance for the previous president to contact them and figure out a way to let him do just that. Interviews have been in person, on zoom, and he prob could come to be a witness.
However, we know he won't, first he would be under oath to tell the truth, we know he can't possibly go four questions without lying. His lawyers would never let him, they value their reputations and like his money to let him do it. What he could do i recommend anyone that was part of the coup attempt in Congress to testify on his behalf, but again we know he won't do that, and they would not participate. That was the problem from the beginning with the republicans decided to not participate.
It's in your court. Put up or shut up.