Howell seems like one of the more likely reclamation projects. The knock on him is he threw a lot of picks his one year playing. Most QBs do struggle in their first year, and then some of them learn and make adjustments and take care of the ball better. Maybe he could do that. He does have the other tools.
So the case for Howell is, he can make plays. He hasn't been bad for more than one year. He can run well when needed.
I mean, maybe it's a 25% chance that he turns into a pretty good starter, but that's a better chance than most of the other options out there.