Fog/light right XC90?

Hello, the fog lamp in the XC 90 is left in the upper part of the bumper. Now I noticed yesterday, that the lamp on the right in the bumper also seems to have an incandescent lamp socket. (looks at it from the outside) This is actually without function, had thought that this only has the function of a reflector. Now the question: If you remodel these two as additional taillight, that is allowed. The function of the fog lamp must of course be preserved, e.g. with a 2 thread light. Technically I can do it, only what the TÜV uncles say about it. Thank you for your opinions in advance. Torsten who likes to rumbast on his vehicles……….