Just sitting here thinking about what I'd love to do with these crazy cars. What about a Mad Max-style point to point through huge winding sand dunes while running from/avoiding military resistance? I guess main thing I'd like to see is more carnage in general. The arena has it for sure, but the carnage is more circular than linear, if that makes sense. The normal races have it too, but often times it's in short bursts rather than a sustained firefight of sorts.
Either way, big ol' sand dune track would be tons of fun. I'm sure someone will come along and say that the physics of the cars would never allow it and I should be ashamed of myself, but dunes man.