I'm not sure you got my point though. If the market runs straight through your sell stop limit order and it doesn't get filled then you are still short and the market can still be falling fast while you are trying to manually exit. In that scenario, you will lose a lot more than the slippage on a stop market order.
Let me take, again, that example of that guy who sold his NEO at $4. But we could take the other example of that guy who got his ETH sold at 10 cents, if it makes it clearer:
https://www.reddit.com/r/ethtrader/comments/6iokzy/gdax_just_sold_a_good_chunk_of_my_ether_at_10/https://www.cnbc.com/2017/06/22/ethereum-price-crash-10-cents-gdax-exchange-after-multimillion-dollar-trade.htmlThat made the news some time ago, and people didn't learn from it.
What did that guy do wrong? HE USED A STOP ORDER. HE DID NOT DO ANYTHING ELSE WRONG.
Wouldn't YOU buy an ETH at 10 cents? Who wouldn't? Do you think that if you had asked the guy "hey dude, you put a stop order there, we're gonna sell your ETH at 10cents now, are you ok with that?" he would have replied YES? Yet, that is exactly the risk you take with a stop order, it shouldn't be there, you should be responsible for the amount of risk you wanna take.
People who place stop orders are idiots who believe that if they place it at 100, they are garanteed to sell at 100.
The only real stop order is a stop limit. If you wanna place a stop at 100, you will probably place your limit at 50, or whatever price you're still confortable selling at. But I SERIOUSLY doubt that you will place your limit at zero, or I don't understand what's wrong with you.
Everyone understands that if something falls from 100 down to 0.1 in a few seconds, it's not normal market behavior, it's just a large dump, or a cascade of stops. Then you'd rather keep your coin, hoping it will go up again, rather than simply losing it.
The guy who placed his stop order and saw all of his ETH sold at 0.1, pretty much lost everything, quite ironic for something called "stop loss", no?
Obviously professionnal traders will tell you that stop orders are useful, because they don't trade things THIS volatile for a living.
I really think all exchanges should at least implement stop+limit, and put limit by default to 50% of the stop price.
There are things that could be done, even though I can't imagine any exchange doing it. Like if an exchange gets into a cascade of stops, it enters a phase of "you can buy, but you can not sell for now", spreading the cascade over time.
For ex, the other day's dip would have been spread over like 10min. For 10min, all the stops would have been processed slowly. Any manual sell order would have been scheduled for after those 10min, but any buy order would have been processed immediately. It's quite sure that the dip wouldn't have been this large. Not only it would have dipped less, but it would have rised back faster because there would have been less fear. And things like the ETH or NEO case would simply have been avoided.
It'd be quite easy for an exchange to implement this "special mode" happening whenever a market falls over x% per second, or something.
That's also what whoever is not an idiot would do, if he had to sell a lot of shares. He would spread it over time, selling little amounts, letting the market go up again. Quite possible that the ETH case wasn't a cascade but just 1 stop on a way too large amount.
An alternate solution would be, whenever a cascade of losses is detected, to average all stop orders. That would be less useful, but it wouldn't produce random big losers.