Without going after Justin Houston for 2015, I think the 3-4 is going to be replaced w the 4-3. We simply cannot keep up w the outside zone playing the way we have on the edges.
While Spike may have a point about pressure from the DL, Tuitt had nearly 20 sacks in his last 2 years at ND and Heyward was also adept at getting pressure at OSU. McLendon is a perfect compliment inside to McCullers in that all he has to do is get 'push' which both he and McCullers seem capable of.
Right now, neither can get 'push' moving laterally like what is required in a 3-4 against a 'stretch zone'. Our ILBs and our proxy ILB (Troy) are 'baited' into lanes allowing cut-back runs which leave only the FS to make the play. This didn't work when we HAD Casey at NT and won't work better now. Foote and Farrior were much better at maintaining their depth against the 'stretch' and 'counters' so they wouldn't get swallowed up.
Truth is, either by 'design' or bad luck, we are better suited for a 4-3 front. Jones could possibly be a Sam but we are ok w Timmons/Williams in the middle. That leaves Shazier our Will. I like it better with either Timmons or Spence at Will (Timmons is a better follower than a signal caller) with Williams(2-downs) and Spence in the middle and Shazier on the Sam. (I suppose we could try Jones at Sam with Shazier in the middle too)
Look at the Bengals 4-3...who do they have really? Geno is a beast in the middle but elsewhere they seem comparable to me:
Dunlap, Peko, Adkins, Gilberry...for us it would be Tuitt, McCullers, McLendon, Heyward
Burfict, Maualuga, Lamur...for us it would be Timmons, Williams/Spence, Shazier
Here is where we need help:
Hall, Iloka, Nelson, Newman...for us it would be Allen, Thomas, Mitchell, Gay (while Allen 'could' turn things around, he's not on Hall's level. Gay could probably 'hang' w Newman, IMO.
If we went into the off-season with a design on going w the 4-3, we still need a competent CB and another 'rush' DE. I think Heyward could do it as well as most but we need a back-up for both sides. (although Josh Mauro was a good DE in college with sacks/TFLs) We also would have our experimental Nick Williams, who looks to be a better fit for a 4-3 DT as well.