I loved Hilary back in the day but they need a respected singer on the panel. I feel like part of the reason for X Factor's lackluster performance last last season is because the audience didn't have enough respect for Demi because of her age and Britney for of various reasons.
And then having 3 women on the panel is not giving the core audience (females) any eye candy.
Simon/Demi/Faith/Ne-Yo or another young male singer would work. Hilary or Jennifer Love Hewitt could co-host with Mario.