Does anyone remember the Dodge Stealth? One of the models had a spoiler (a small one, about 2 to 3 inches deep and full width) at the leading edge of the rear decklip. That is the kind of spoiler I would want on the Intrepid. That would help to maintain laminar air flow of the rear, and could reduce lift/drag on the rear. Due to the virtual axis trunk hinge, the spoiler would not hit the rear glass when trunk is open.
That might look kinda cool on a trep. I would have to see a pic or a photoshop though. But I don't think you need a functional spoiler on a FWD car. I may photoshop that on a second gen Intrepid tomorrow. I am kinda curious how that would look.