I took Corona up on their offer, “We are making extended Corona Enterprise trials available for plugin developers” made in this post:
https://coronalabs.com/blog/2015/04/01/open-source-plugins-and-coming-soon-corona-store/
Currently, I am working on an open source iOS GameKit Corona plugin for iOS 7 and greater that will expose to Lua most of the GameKit Framework. So far I’ve got Leaderboards, Achievements, Challenges and Real-Time Multiplayer working with custom Corona UIs and the Game Center UI. After I get Turn-Based Gaming working I’ll open it up to the Corona community for feedback and testing.
Corona Enterprise is a bit of a learning curve for plugin development: for iOS alone you need to know Xcode, Objective C++, MRR (ARC is not supported), C/C++ and the Lua C API. Along with the Quickstart Tutorials, the Corona open sourced plugins really help with the learning process: https://github.com/coronalabs/plugins-source
After I finish the GameKit Corona plugin and release my game that relies on Game Center Real-Time Multiplayer, I plan on making a GPGS Corona plugin for Android and iOS.