We need a custom applet for TomatoUSB or DD-WRT. This applet will add a new menu to the interface and it will enable the user to configure the VPN settings in a custom menu. Other companies do this easily, they are doing it in tomatousb by using wget to direct the router to download and run a .js applet which executes commands to make this possible,
TomatoUSB has the ability to run a VPN integrated, we just a custom tab in the interface to add our logo and allow the user to enter their vpn credentials there, once they do that, it will connect to the VPN.
This is not a big job but it is outside of our hands. We can show you how another provider does it, should be very easy to reverse engineer.