Yeah man! Now that you're mentioning it, even in single player mode it would be cool to be able to choose who you're playing - the one who's getting chased, or the chaser himself.
The only thing here is how would they limit the city. Because with the other player controlling the car that is being chased, he can basically go anywhere. However, if he's the chaser, the area could be more limited with a system like in DSF - if you're too far away from the other car, you've lost. Which means you can't get that far away. It would need like some (red) walls like in DSF - but I think that would limit the area too much, also like in DSF multiplayer takedown. Maybe with next-gen it will be possible to just make these city areas bigger. And then say limit the time to 1 minute 30, and make that area only so big that from wherever you start, you will reach the limits of the area within 1 minute 30. I don't know, we'll have to see!
By the way - talking about supernatural nature. I'm wondering how they will do this if they add shift again, because Tanners out of the coma now.
Also a thing I'd like to say - I do think the game is realistic, but the part in which Tanner is in the coma (well most of the game) IS actually realistic - because he's in the hospital and the TV is on. It's all a psychological thing, and it can happen in reality too - what he hears enters the subconcious part of his brain, and that's where he dreams. And in his dreams, anything can happen. So I don't think that part is too unrealistic. In reviews and on various sites, they always talk about a superhero Tanner and blabla... this is all wrong, it's just a coma, and if people would research what happens during a coma on Google, they wouldn't be talking crap - so those reviewers are obviously very close minded. Just wanted to say that

So in order to keep the realism it had now, it will be difficult, without having Tanner falling in a third (or second?) coma hehe.