Like Quickfire stated ejectors are legal for NCOWS. This is one of the things that has bothered me about SASS. My 1895 Montgomery Wards catalog shows several. My 1897 Sears & Roebuck shows many. They must have become more popular in two years. Of course this means your impression should be from that era.
As for single shots, as long as they have the opening lever we are use to seeing on doubles and not the push button like those on the H&R Topper they are legal. No one has been able to document the latter.
As far as being handicapped, not as much as you might think. I have seen people use them with extra shell between their fingers do very well, in fact a good friend of mine can regularly hit the clay bird that is launched in the air after you knock down the plate. You have to load darn fast to be able to do that.
Will Ketchum