Another solution would be for people to make up their minds. Maybe it's time to give up entirely on multi-tasking support in the OS, because what's the point if all interoperability is going to be disabled "for security"? Might as well just go back to running one program at a time and close up all those security holes in one go.
Why everything has to be on the server? ok, Where are you going to store your client authentication tokens or decryption keys. A proper file system isolation is a key if you want a proper application sandboxing