not an issue IMO
Career wise it's almost always better to coordinate than be a position coach. Whether you have been one or not before. Your one of 32 doing that at the highest level in the world. Next step down you are in a tier of about 500+ NFL position coaches. There are exceptions but I don't count here as one.
Money could easily be double the pay or more for most guys.
You're going to a solid contender with one of the best records in the NFL the past 7 years. The Saints are now thought of as a solidly run organization and desirable destination. That wasn't always the case. Some franchises this could be true of. Payton staying in Dallas versus taking the Oakland job in 2005 for example. Good story btw
The overall organization is a much bigger factor than the state of the squad IMO.
As others said, you're teaming with one of the most prolific offenses in NFL history. Great defense would be fine but if you can get it just to average range you are talking about immediate Super Bowl contention. All GW had to do was improve the defensive rank by 6 and that happened.
There's no avoiding how much of a total meltdown the D was last year. The great majority here thought the defensive personnel moves in the offseason were a distinct improvement over 2011. For whatever reason the scheme stunk and did not work. As fast as it fell off from 24th to 32nd in yds allowed and 13th to 31st in points allowed there is certainly the potential to turn those back around in one season.
In retrospect I think last year will go down as a giant asterisk in Saints history. We'll never be able to quantify the damage done by Bountyfarce but it was more significant than most would have imagined before the season.