You know about Achille's rusty heel in these cars, I'm sure (front control arm mount area).
Another mod I've been meaning to do that's showing up on more and more aero-focused production cars is clean up the bumper corner, behind the rear wheel:
The Mirage's Cd for the Canada/US model is just 0.28 according to the company. Pretty decent for a little hatchback (notice also the mini-kammback spoiler and the smooth wheelcovers). This sharp bumper corner treatment that promotes clean flow separation is getting more popular.