NW.js 0.13.0-beta2 is out, and with the next beta of C2, it's looking like most of the integration issues are solved, so the NW.js side of things seems to be working smoothly now.
However it appears Greenworks doesn't yet support the 0.13 branch yet. Their page only mentions 0.12 support and I get an error trying to use it with 0.13. I've logged an issue on their github here: https://github.com/greenheartgames/greenworks/issues/64 and sent the team an email to check on the support status. So the next beta will not have Greenworks support still, but when we sort out Greenworks support for 0.13 we should be able to update the plugin again (and hopefully add more of the latest Greenworks features).
For shipping the plugin with C2, I'm hopeful the release after the next beta can be a stable. If this is the case, I avoid making any serious changes for a stable release (had too many disasters in the past with that), so even if the Greenworks plugin is working before then I'd postpone shipping it in C2 to the next beta release after that. Still it shouldn't matter much if there's an updated plugin you can install separately.