Apart from it would be annoying having to drill them out every time you wanted to take a wheel arch off, I can't see any reason not to. Probably more secure than the plastic crap. I was interested in doing it too but the mounting holes on mine aren't quite up to using rivets on
I've pop riveted and used the plastic clips, out of the two methods I would say plastic clips all day long, once you have the first 2 in, it's plain sailing. Pop riveting was a really pain and took ages!