Only morons use stops without limits. If you're trading something that must be sold at ANY price, you shouldn't be in it to begin with.
The simple solution is to halt the market or the specific stock when there is near zero liquidity. How hard it that to implement? Nobody gets hurt from no trades. Heck, open the market half an hour a day if there is no liquidity. The problem with HFT is they got too much time on their hands.
May 6th happened for only one logical reason. Warren Buffet called a special someone about a certain stock he wanted to buy but he missed the price. That special someone asked at what price did he want to get in. Mr Buffet replied well I would love to get in at .01. Special someone said ok, give me 5 minutes. Only one man in the world can make what happened on May 6th actually happen, you guess it, Mr. Chuck Norris, he can move the market to wherever he wants