I don't really know real world circuts very well, but:
Bathurst: I read about it somewhere, it sounds like a pretty cool course. I just checked out a map, but maps don't really tell you anything about how a circut is to drive.
Pike's Peak: Anyone who doesn't think this should be in the game should find some way to get and watch Climb Dance with Ari Vatanen. (or if you already have the ubiquitous "crawling in the dark rally drift movie", all the good bits of that are from Climb Dance.
)
the Vancouver Indy circut: It looks
like this. Yeah, I just want some track that's in my area. It's a good one though.
Nurburgring GP circut: Pretty obvious addition if you ask me.
Nurburgring Südschleife:
Read about it here. Some people would argue that if there's one thing the 'ring doesn't need, it's more track, but this would be a good idea just for the historical intrest.
Fuji Speedway '60s: Yes, there's yet another variation.
More info and map.
Fiorano: If they finally get the Ferrari licence, they've got to put this in.
Maybe as some special deal with some manufacturer, they could put that company's proving grounds in the game. I think that'd be really cool.
This is supposed to be GM's Arizona facility, but it doesn't seem to be loading for me.
(linked from
here)