I just tried a technique I've used to partially fix scratched plastic eyeglasses, and it worked quite well on some PCGS slabs I have. The first thing you need to do is get some furniture wax. You have to make sure you get real wax, and not one of the "non-wax" versions. It's the Carnauba wax that does the work. Then, you just wax the clear parts of the slab, you rub a small dab of wax into it with your finger, and then polish it with a cotton cloth. It makes the scratches and scuffs about half as noticable, and it gives the plasic a more water-clear look. I'm surprised none of the grading services offer optically-coated slabs, it would make it much easier to see the coins, and it might prevent some outgassing of the slab on the inside. It would also make them much more scratch resistant. This could really give one of them a competitive advantage.
Perhaps optic coated slabs are a good idea, but imagine - what happen if you hear this: add extra 7 dollars for extra scratch protection. Price of slabbing is quite expensive in my opinion. Now I wish some slabbing company is to do it offshore to make it a bargain - shipping prices and high USD actually drive away considerable number overseas people to slab. Overall: only the upper end collectors may want to consider this, but in reality, if the value of their coins are so high, they would actually store them in a better manner.
It probly would be an add-on, and of course they'd love that. At the other end, what would be nice is a service to authenticate-only, or to authenticate-and-grade, with no slabbing.
If you are concerned about scratches on a slab try a buffing wheel. Use a very soft buffing wheel at a slow speed if possible. This, if done gradually, will slowly and almost insignificently melt the plastic back into a smooth clear material. I've found that putting such a buffing wheel on a bench grinder has to much speed and is also rather dangerous. Same with most one speed drills. What I did is to make a reostatically controlled portable receptable, mount a one speed drill to a work bench with the buffing wheel in it and turn on and lock the trigger in place and use the speed controller to run at just the right speed. I first noticed that this is a possibility when I used a saber saw to cut open a slabbed coin. At to high a speed the plastic just melted back together as fast as I cut. This indicated that the plastic is soft enough to be melted slightly with a slow buffing whee. It works. What was weird was after I removed some scratches from a slab, I ended up cutting it open anyway.
