You might have to install dd-wrt on a router beefy enough to run a VPN client. That way your ATV doesn't need to understand VPN.

This would be a really interesting experiment. Measure downlink speeds over a fully VPNd connection.

This was on HN recently, though it sounds like there's more experimentation to be done.. http://mattvukas.com/2014/02/10/comcast-definitely-throttlin...