What if Tommen pardoned Tyrion?

I’m gonna go over the show canon as I believe Tommen is 8 in the books I think? And wouldn’t have a ton of authority, But for this scenario I’m thinking at the start of Tyrion’s trial Tommen instead of recusing himself from the trial he would say

“My lords and ladies I Tommen of the house Baratheon, first of my name, king of the Andals, the Roynar, and the first men. I hear by pardon Tyrion of the house Lannister of all crimes.”

What happens? I don’t think Tywin or Cersei could exactly do anything in that moment since it would happen in a public area. But still would love to hear everyone’s thoughts on this.