OK I agree with painting the fillers. I was leaning that way to start with. That leaves mounting the license plate. The snap into the fiarlead idea doesn't look like it will work for me since I have a safety thimble with cushion that sticks out 3". I don't think I can put it behind the top lip of the fairlead either. I have a SW fairlead that is just an oval, no extended portion at the top.
I still don't see any issue with drilling new holes for the plate so it will be located right above the fairlead. The location doesn't appear structural and assuming I properly finish the holes so they won't rust.