Something I just thought of. One team that (potentially) could be pretty good is the Broncos. I say that very hesitantly because they have a new HC who has never been a HC before so we have no idea how he'll do.
If he ends up being all that, at least defensively, then that should make things interesting. Flacco has a higher upside than Keenum IMO, and more importantly, they now have the Steeler's o-line coach (has consistently had a successful record putting up good o-lines).
I'm far from certain that the Broncos will be great, but the upside is there. They could potentially improve on both sides of the ball, which would obviously make them a solid team.