While I don't specifically have an example to show you. I've used the Open Authentication Module in the app store to implement authentication with google and linkedin. Not sure if it's easier than whatever your current set up is into an OAuth 2.0 setup.
I have accomplished this using a module from @PimvanderNoll as a starting point. I built OAuth2 authentication against Microsoft Dynamics CRM using a combination of REST request Java actions (from the REST module) and Deeplink request handlers to handle responses from Microsoft Dynamics. I didn't do any Java customization.
The app is in Mendix 7.6. If you're interested in having a look at it, let me know and I will get it to you.