Even if we want to build a Seahawks' like defense, it will take several years. They stockpiled picks, very much like the 49ers did, over mainly 3 years.
2009 - Max Unger
2010 - Earl Thomas, Golden Tate, Russell Okung, Kam Chancellor
2011 - James Carpenter, Malcolm Smith, Richard Sherman, K.J. Wright
2012 - Russell Wilson, Bobby Wagner, Bruce Irvin, J R Sweezy
UDFA Brandon Browner, FA pick up Marshawn Lynch
Unless we hit on our draft picks at that high of a rate over 3 years, and have a QB like RW play at a high level, we will have to supplement with free agency. I am using a team that primarily got built via draft picks.