I would love to see someone recreate a 70s style talk show, where it isn't merely about who has a TV show/movie/book to promote, it was about putting people together and bouncing them off each other. Often substance-enhanced. I think talk shows became lamer once they started bringing on one guest, solo, then the next. I always liked the Mike Douglas set up where each guest got his face time with Mike then moved down a chair for the next one to come in, and everyone would all kibbitz. And the people who were fun kibbitzers (or entertainingly f-ed up) came back again and again.
And I wish talk shows in general would cast a wider net--Harlan Ellison used to be a regular talk show guest in the 70s. Can you imagine any science fiction or fantasy author getting on a talk show now?
As for Leno, I've never liked him at all. He should just take his gazillions from the last 20 years and retire with some dignity left.