As the title says, make it possible to make the cutouts in plastic, chrome, paint or carbon, too.
This way you can add licenseplate holders which are made of different materials. I personally would love to add a black/grey plastic cutout.
Also, do they have to be center-aligned? As I sometimes like cars to have the licenseplate in a square to the side (Lancer EVO) or just a regular plate to the side (Alfa Romeo)
On the given examples, they are properly off, I think. Couldn’t find a picture this quick but there is even an Alfa Romeo where the licenplate actually ‘curves’ around the left front corner of the cars bumper.
So will these cut-outs be in or out? Do you really have to make them center aligned? I see a possibility to use these cutouts also alternatively than just licenseplate holders