Much as I like Sandi - I’ve never really seen her do much ‘serious’. I think she’d be a bit of a waste as part of her ‘charm’ is going off on a tangent. I think 15 to 1 completely lost the plot when it was revived and expanded from half an hour to an hour, with her commenting after almost every question was answered.
Perhaps it doesn’t need to be someone famous, but definitely, as already said, someone in for the long-haul. It’s not a programme given to chopping and changing, IMO.