[indubitable]

Of course you're right, but the review process is connected to the journal. PLoS journals are very accepting and so they end up being seen as a repository for publications that could not get published elsewhere. That's not to say nothing of value is published there, but rather that if you take a random paper from one of their journals, it's going to be of a different quality than a random paper from the Annual Review of Astronomy and Astrophysics.

And like others have mentioned, a supplement is a great idea because of publication bias against things like negative results. However, I would again see this as supplementing and supplanting when I think most people here are gunning for the latter.