I think more than anything, GB needs a good podcast host. Ryan was always so good at keeping the flow going in the podcast, pulling back the discussion when it got a little bit too ridiculous, and keeping focus; Jeff just doesn't do that as well. Maybe Ryan was that special guy who had all the right qualities for the job and is irreplaceable. I can't think of anyone offhand who could fill his shoes, the person who is equal to Jeff and can put him in check when need be (no disrespect to Jeff intended).
Gies is a good guy, but after a while some of his politics get tiresome, even if I share most of his views. By all accounts, he is very happy at Polygon and probably wouldn't leave anyway.
Garnett Lee is an interesting choice, but I wonder if he would really fit. I don't think Shawn Elliot would really fit either.
O'Dwyer seems like an obvious choice, but he is needed at Gamespot and CBSi probably wouldn't let GB poach him.
I guess no one really leaps to my mind, but I suppose we'll find out sooner rather than later.