You need to be using Extension Mobility so that the ACD DN is on the Device Profile only; or, IP Communicator exclusively. We use IP Communicator for our call center as it saves the cost of physical phones. Unplugging the physical phone does not actually solve the problem which is you have more than one line appearance of the ACD DN. This has never been supported; CCX 8 just began enforcing more of the rules to avoid needless TAC cases.
As for the AnyConnect-based phone VPN client, there are a lot of things that the BU doesn't test. Last I asked there was not a specific release comitted to add support for this. You should speak with your Cisco AM to submit this as a feature request; if customers do not ask for it, it will never happen. Similar to your unplugging-the-phone trick, if you're willing to self-support and can make it work, feel free to use the AnyConnect-based phone VPN.