I merely provided a way that they could make a counter argument in your doomsday scenario where every other exchange tried to take advantage of a good will statement they made to protect the interests of their current customers. Whatever the courts (yes it would be plural) decide to do in that situation is anyone's guess (including mine).
The kind of arguments you are making in this entire debate are the same kinds of arguments made by people who say that if bitcoin collapsed it would pull down the world's economy. Even though there is vastly more evidence countering those beliefs. However, it can never be known for certain unless such an event actually happens. Which both that one and this current one you are suggesting will likely never happen.
Which is unfortunate for purposes of this debate. ;)