(...) My first thought was rotating the original fixture by 180 degrees and attaching it from below – Would you think this is possible?
Cheers
Sven
I don't think so. The upper number plate holder and the lower part, where the fog- and backup light are mounted, is one piece.
It's made from plastic, so it was very easy, to cut the plate holder of. After having done that, I attached the number plate with a stainless steel angle. As mentioned before "tinker"
I'll take some close-up pictures

and post them soon.
Sunny greetings,
Ivo