Really? A rallycross track on South City would be pretty weird, unless it's on some sort of construction site or something.
I'll probably get blown to peices for this but a Dual Carrigeway or Motorway track would be nice, a ring road, that is. Let's say it would be shortened down to about 10 miles, it'd make a good Cruise Server as well as a nice Drag strip thing and a place to test the cars top speed if a proper tuning program replaces LFSTweak.