mad_crease: I think you could run it on your system but there would be some areas with FPS issues.
Nexus has a few mods that can cut down things outside the baked in parameters. Mods that take out the distant cars etc.
You will experience some delays, as your hard drive is probably not even 10K rpm (or better). Slower hard drive, less hardware/bandwidth/power - it will all lead to data processing delays. But, i think it would be playable. To me, the game is not worth playing if you can't take advantage of the world environment. The visuals. They got that right IMO. If you elect to shut that down, your total game enjoyment will be much less.
i have three SSD's totaling 3 terabytes gave up spinners years ago.
think i will wait though.