how about this fix. a wallet that has a built in hedge. it automatically goes short against your balance so you are flat neither long nor short. your dollar equivalent stays the same.
Sounds like a recipe for utter disaster.
The Mycelium wallet does have a service named Coinapult locks in it that allowed you to convert to USD in wallet and then switch back seamlessly. I'm not sure whether it's still going and there've been some complaints about it.
Converting back and forth between USD also creates a tax liability in a few countries. As can shorting too.