I would like to suggest to add the co-author-plus plugin functionality to wordpress Out-of-the-box.
I think co-authoring should be supported by default. The simplicity of this feature is very much alike the simplicity of wordpress, and i think it can be a feature that will be used by a lot of multi-authoring blogs (and there is a bunch of those...)
every company blog cloud publish co-authored posts, with credit for both authors. every academic or semi-academic blog will use this feature.