what if there was a USB adapter that had a little chip in it that routed anything that passed through it directly to and from the sandboxed environment?
You can alter the rate of transmission for different types of traffic. This is one of the benefits of the packet system. For example, if you wanted to rate limit peer-to-peer connections but not peer-to-giant-corporation connections, all you'd have to do is modify the QoS settings on your router. You can do this at home.
you've realized that the problems are not impossible, and it's just a matter of getting people to think about them in the right way.
that's easy. Humans have been getting other humans to think the ways they want since the written word. Nothing is more practiced as a discipline, except perhaps prostitution.