I have an idea about combining several ideas into one track. Many people here want the Nürburgring (Nordschleife) as a track or something similar. I've also seen quite a few people here and in other posts ask for a hill climb and also a forest road you can drive on. All of these ideas can be combined into one track.
The issue with a really long track is that it may get boring and you need many cars in a race to make it seem like you are actually racing. What good is racing if there is 1/2 mile between each car? You might as well drive solo on an empty track
My idea is to combine some of the elements(turns and similar track sections) of the Nürburgring into a track that has a section that goes up and down a mountain. That way you also get your hillclimb tracks and a forest road.
As for the mountain, I'm not talking about a 15,000' tall peak, but more like the lower section of a mountain surrounded by hilly some land. Maybe have a 1000' elevation change for the section used as the hill climb going up the side of the mountain. That section can also be incorporated into the track and add the challenge of going back down the side of mountain. The rest of the track can be off the mountain on a hilly section of land. The track can have the appearance that its not a permanent track by having the hillclimb section appear as pavement with a dividing line down the middle. Also, there can be a dirt road going up the mountain to use for rallycross and an off road hill climb section.
To keep the people happy that want a long track, there could be a configuration that is 5+ miles along with several shorter configurations.
I have a general idea of the layout and need to put it in a picture form.