first thing that came to mind was an image capture system that could take images from a ccd camera, and extract the locations of hits, and score them according to a preset standard target placement.

I think your great idea sank well in my brains, this method would be most reliable because i always subtract the previous picture of my target and see the difference.
this way the target lasts for a long time and it is maintenance free.
It also saves on hardware problems and wirring and installation problems.
Well done Dennis, I will give you some credit if the project came to life and made some money.
Regards
Mahmood