The pitch is simple, "Mission: Impossible with crooks". Each week they get together and pull off some elaborate heist. Clooney, Pitt and Damon are probably all too expensive to pull in for a project like this but I'd think the majority of the remaining cast would be up for it. You have a large enough ensemble cast to spend quality time exploring each of their individual personalities, quirks, past histories, old loves, old enemies... and because you have a selection of skills to pick from, not all of them need appear in each episode, which allows for some flexibility and creativity in the storytelling.
(Update: several people are telling me that the series Hustle is pretty much what I'm describing here? Likewise Leverage.)