For a sequel, I would not want it to be set in LA at all. I would want Chicago during Prohibition (inspired by classic gangster films and more modern works like The Untochables), New York in the 70's to early 80's (gritty, dirty, dingy, pre Giuliani NYC), or maybe something set in England in the late 1800s....either a Sherlock Holmes license or an original character in that same spirit.
Another nice touch would be if MS allowed the Xbox to create, at your request, a custom games marketplace that only showed non-purchased content for games on your played games list. I would LOVE that. I hate when I'm away for a week or two and come back to the console and spend forever trying to simply check if anything interesting hit the marketplace.