Lakc, I was wondering about that myself. I know I've used some of the old heavy duty paper shears before and thought they might work for the thin stuff I need to cut. .016 brass and .020 aluminum is probably the top of the thickness range I would need to cut and it wouldn't be that often. Most of the stuff is .005 to .010 brass. I might try to find an old paper shear on craigslist etc. and try it out. If it's cheap enough, what could it harm?
Paper shear will certainly work, you can even cut sheet meet a with regular old desk shears in a pinch. Most paper shears will also help you with keeping things square. The big problem with paper shears is the safety aspect, especially if you are putting your back into it to cut metal. I would tend to discourage people from doing so regularly simply because those old paper shears are known hazards. Considering the thickness you are talking about a rotary paper shear might do the job, I have not tried that approach though.
So to answer your question what harm could it do, you could end up with short fingers.