I know this may be too late (most likely it is), but this is for others mainly.
I found a solution for my own needs. I did not end up using a script. I use PIA (PrivateInternetAccess) for my VPN client through the Asus RT-N56U router with Padavan FW.
For the WAN settings, I changed the connection type to L2TP. This allowed me to enter my client information into the fields that popped up below. I tried PPTP, but the connection speed was significantly slower. . . Some people may dislike this, but it works for me.
I checked the log as the connection was established to make sure there were no issues with this method. Nothing seemed to arise.
I had attempted a connection through the "VPN Client" tab with no success. The connection was dropped over and over again by the VPN provider.
Using the L2TP connection, I have had a continuous connection with awesome speeds. Currently, I'm getting 50Mb/s, which is the max of my ISP.
Let me know if you have any questions!
In order to get this to work:
Log into your PIA account through their website. (https://www.privateinternetaccess.com
At the bottom of the screen (after you log in) there should be a green box that says
PPTP/L2TP/SOCKS Username and Password (Optional)
Click on: “Generate Username and Password”
Whatever Username and Password that gives you is what needs to put put into the router’s login information.