How about Clint Eastwood sitting in Nancy’s chair. Formerly empty chair.
Expanding on your thought - If he doesn’t give the SOTU in the House chamber, then he can assign the seating in whatever way he likes, I would think. He can put all those angel parents right behind him, the Covington kids, etc. Some active duty Marines, Clint Eastwood and the other paltry few from Hollywood.... and so on.
He can say that all of the Senators have to sit on one side and all of the Representatives have to sit on the other... He can make them double up on seats, if he wants. He can make sure the big bank of EMPTY Dem seats are front and center. This could be fun.
How about Trump giving the speech with an empty desk and a gavel atop....right in back of Trump. Maybe even add a portrait of her.