While some of the proposed changes (e.g., better draw distance, more detail, etc.) aim to make the game better on modern hardware, it seems like adding things like "denser traffic" would have the effect of changing the gameplay itself. While denser traffic would certainly make the game's Southern California setting a little bit more realistic, I'm not sure that it would make the game more enjoyable. In particular, it seems like a change of this nature could make some of the game's high-speed chase missions and side events into a big pain in the ass.
The fact that you can do something doesn't necessarily mean that you should.