Your question is not so much about an individual, but more about the Seahawks current style of football right?
There is one X-factor that many people are missing: team mentality and team love. That is something VERY hard to duplicate.
How else do you inspire those that were deemed not good enough to draft early? Or the unwanted from other teams rosters? If it was just one or two players, that might be coincidence. But it is an entire team.
Marshawn is the best example. If you see this guy, he appreciates the respect and team love he gets and responds in kind. He plays not just for himself but for the entire team and for his coach.
Another great example: team defense. Guys really rooting for each other. Guys preparing together giving us one of the best route recognition team defenses.
That kind of mindset lifts someone to a whole new level. And it comes from leadership: Russell, Coach, JS, etc. So as long as the leadership is there (and Russell Wilson: a big part of that) the Seahawks will have something many teams won't have regardless of the individuals that get signed.