Rison
Wahoo!
To me, the appeal of seeing Gretel/Davina in a CBB is to see how someone who let Big Brother completely consume their lives for three months each years and spent so much of their own time watching footage and discussing the show, to see how they would play the game after watching so many different strategies etc.I'd honestly love to see international hosts come in the house. I love your idea of seeing Julie Chem come into the house!
Because of the different rules in BBUS/CA, seeing Julie Chen in CBBAU would be less rewarding - since it's a completely different game.