Windy is right. Dalton makes a good fit for a viable veteran backup if Mitch fails, if you don't give up high picks and the cost is reasonable.
The positives
1. Coached by Bill Lazor and had his best seasons with him
2. He's capable of actually throwing the ball and putting up yardage. Multiple 4000 yard seasons or at least averaged 250+ a game on short seasons. Actually had a season with 106 rating. So you at least know his ceiling is good and he's capable of being efficient and passing on teams. The knock is that he hasn't done that enough and wasn't good last year.
3. At least he's shown his upside. He started his career with 5 winning seasons but obviously ended up mostly playing Patriots, Broncos, Steelers or Ravens in AFC playoffs so knock his playoff beats, but still won games on a mediocre team. So you know he can win if he has some level of talent, especially a defense.
He'd be a step above unproven guys we've always signed in the past like Hoyer, Glennon, Campbell, Daniel that never had good seasons. We just hoped they would somehow improve. Dalton has at least proven he's capable of playing well.