I've seen similar questions all with no answers, so I'll try to be specific.
The purpose is for increased privacy, in case the VPN service should turn over logs to law enforcement. You may be a political dissident, and only enjoy privacy until you violate a law in the country where the VPN service is registered or a more corrupt government comes into power.
can you use a service like hidemyass, stacked on top of ipvanish.
eg: configure ipvanish through the mac osx preferences as l2tp, and the second one using the hidemyass vpn app.
so websites you visit see hidemyass, but hidemyass only sees ipvanish ip.
not sure how to go about this.