The Jaguars have no player on their defense that warrants building around more than a player selected No. 2 overall in the 2013 NFL Draft.
I'm a believer that the difference in the 3-4 and 4-3 defenses is marginal and that good players will make a defense good, not scheme. The top three defenses in 2012, in terms of scoring, were the 4-3 defense of the Chicago Bears, the 3-4 unit of the San Francisco 49ers and the 4-3/3-4 hybrid defense of the Seattle Seahawks. Tremendous players in each of those defenses are what make the units the elite groups that they are, not the playbooks.
That's why the Jaguars are in the perfect situation to be whatever defense they want to be in 2013. Presumably there won't be a quarterback worth taking with the second overall selection, leaving the Jaguars with a selection that will almost certainly be used on the defensive side of the ball.
Forget the schemes, forget the holes, draft the best player for that spot. Whether that's determined to be Dion Jordan, Damontre Moore, Bjoern Werner, Jarvis Jones, Star Lotulelei, or another player, take a player and build from there. Whether it's a 4-3 defensive end, a 3-4 outside linebacker or another position, the Jaguars have the opportunity to start with a clean slate and build around that player.
Yes, the Jaguars have some players under contract on defense that may not benefit tremendously from the switch, but do they really have someone whom they've made a big enough investment in, so as to avoid building around the No. 2 overall selection in the 2013 NFL Draft? The answer to that is a resounding no.