Here's an interesting variation on a license plate holder from a German Web site. It sells for 48 Euros, or about $59 USD. Now if only their RX-8 bumper didn't remind me of a main battle tank...
http://www.ath-hinsberger.com/ (click on Products)

Probably wouldn't work very well with the stock front.

Worst design ever, the front vent is half functional as it depends on the front air damn, below the grille, to get its air circulation.

My thought exactly. If you look into the front vent you'll see the radiator way back there.

With that plexiglass backing plate it looks like you could run a nice bead of caulking and just seal the opening completely. Why bother allowing any air to get to the radiator at all?