Imagine the scene:
You've reduced the light output of your lights. Poor weather means you give it more beans than you should, and it's at night. You end up writing your car off, and in the process you cripple Harry Kane who happened to be driving a car on the same street and you had a coming together.
Insurance man comes to check on the car as Mr Kane is putting in a multi-million pound claim for his useless legs, when they discover that you've reduced the usability of your lights. Suddenly you have no insurance cover, and every one is coming after you for everything.
Seriously, don't bother. The MOT issue isn't worth worrying about, insurance most definitely is. If you really must, for shows and that, i'd be grabbing some stick on stuff that you can throw on during the day and then removing for the drive home.