Hello, I have experience working with openVPN. The way I would do the client is building a python graphical user interface over the normal openvpn client. To the best of my knowledge the big vpn provides to the same so to keep everything up to date easily, so you can update the client/server separate from the user interface.
I'm available on Skype to discuss the project in more detail.
Feel free to contact me on the chat if you want to tell me more about the project or have any questions.
Thank you,
Stan D.