This could be an entirely legit move in a free market. The exchange is just the platform. They must now be allowed to get in the middle of trades. That means if someone comes in and sells $50m of Ether, that's fine and the price will crash.

It's up to the traders to react to the market as prices change.
Stop and limit orders are a way to protect yourself as a trader. This is where the exchange gets into trouble if the system doesn't close trades at the requested price, people get upset.

Your strategy is sound though. Put an order on the books to buy $1,000 worth of Ether at $10. Then just leave it there in case it happens again.

The only downside there is that you'll have $1,000 forth of Ether locked up waiting for that trade to trigger.