Realistically, switching to a 3-4 personnel wise is not that difficult assuming we adopt a 3-4 like the Texans. In their scheme JJ Watt still plays a one gap scheme in which case both Melton and Peppers would make good ends in that type of 3-4 scheme with Idonije backing them up. We would need to draft or sign a true NT. As far as LBs, Briggs and Urlacher are fully capable of playing ILB in such a scheme and McClelin is fine as one OLB. So the only issue would be whether Wooten could drop maybe 10-15 pounds and cover well enough for the other outside LB spot and getting more depth at LB.
Having said that, worrying about the one aspect of the team that is top 5-10 in the league seems pretty silly to me with all the problems on offense.