I already have most of the new REST API implemented in libkgapi (note to myself: push it!), writing a resource around that that would support 2FA and Gmail's weird workflows would be most welcomed by many users, and should not be that much work.

I already implemented the resource once, turned out that the biggest problem was to handle the "everything is a virtual collection" concept in KMail, which looks on virtual collections almost exclusively as search collections, making interaction with the GMail stuff hard for users.

As suggested, this should eventually be merged with the Calendar and Contacts resource to provide a unified Google Groupware resource.