The key to remember here is that the 3300 does not support NAT translations by itself... If you have a hardware VPN to employees homes, then yes it should work. If they are connecting a client software to your corporate network, you MIGHT be able to get it to work with Internet Connection Sharing of your computer, but that is hit and miss at best even for technicians, for a regular end user, I really wouldn't recommend it.
Rather than using a hardware device, if the remote computers already have a VPN connection, you could likely just us a SIP softphone like Bria or X-Lite much easier than trying to make a soft vpn work for a PC and phone at the same time.
Like wiseguy said though, a MBG would be a simple way to allow phones to be moved outside of the firewall and securely connect back to the system from anywhere in the world.