Nice to meet you on freelancer.
To be honest, I don't have experiences with google app or google API etc. I am an experienced C# programmer.
But I think there maybe another way you want to try. Obviously, we can change the permission of the sites through google control panel (or some similar web pages on google), correct? So we may create a bot to do this operation automatically through a WEB AUTOMATION FRAMEWORK.
One most popular such framework is : Selenium.
When it run, it will start Browser window, login automatically, fill blanks, select drop down etc, it can do anything could be done manually.
But I don't know how to bypass captcha, let me know whether captcha will be encountered
Thank you!