I'd LOVE this.
I rode to a couple Nats games last season and locked my bike to a pole and to a barricade. I unclipped all the lights and seatbag and carried them with my helmet into the stadium. It was a little inconvenient carrying that stuff, but I always was unsure about the safety of the bike itself.
I really like the idea of handing off my bike, getting a numbered ticket, and knowing that I can retrieve it after the game. It felt sketchy enough at RFK, but I wouldn't go to the new stadium on my bike if I didn't have someplace safe for it. I have a feeling that there will be even more cyclists riding to games than in the past.