Well, my problem is that I wouldn't recognize half the actors they might pick. Robert Downey Jr might be fun, though. In the batsuit, some wouldn't recognize him at all, and some not until he spoke. Some wouldn't think anything of it, but a few would refuse to believe it.
Inner voice: "Someone from the Marvel universe can't be a DC character, so that can't really be Tony Stark in the Batman outfit, because Batman is Bruce Wayne.
-- But wait, it could be that Tony Stark, a multi-billionaire playboy, might disguise himself as Batman to travel incognito! Or maybe a Marvel character can wear a DC costume because in the Marvel universe DC super-heroes are fictional. No wait, they're both fictional."
Then his head would explode.
Inner voice: "Someone from the Marvel universe can't be a DC character, so that can't really be Tony Stark in the Batman outfit, because Batman is Bruce Wayne.
-- But wait, it could be that Tony Stark, a multi-billionaire playboy, might disguise himself as Batman to travel incognito! Or maybe a Marvel character can wear a DC costume because in the Marvel universe DC super-heroes are fictional. No wait, they're both fictional."
Then his head would explode.