So I want to use a payment gateway such as CCavenue for accepting monthly/quarterly/yearly paid memberships which expire if not renewed. I understand that I will have to get some custom development done to implement the payment gateway. Who are the possible developers who can work on this? What I am not sure about is whether to use the existing Account upgrade option or to use some add-on. Can the existing systems be extended to take payments through a payment gateway besides Paypal? Any tips on how to go about this and experiences would be helpful.