I learned that, if we had a few more LBs, or possibly moved some Safeties to OLB, we could run a pretty good 3-4 defense and a cover 4 secondary.
In the 3-4 defense, your down linemen are supposed to be bigger, run stopping kind of guys. VV would make an excellent nose tackle in this role. Collins would make a good run stopping DE in this system, as would Gangwish or Freedom Akinmoladun. These guys focus on penetration and stopping the inside runs, and in passing situations they take up blockers in the middle, collapse the pocket from the middle, and prevent mobile QB from scrambling up the middle.
The OLB should be converted safeties, both for pass rush and to cover the flats. Also, they should have some speed to chase down opponents running outside. MLB should be run stoppers with just enough speed to chase outside runs and prevent a cutback.
The secondaries, even the new safeties, should be built like and able to run like CBs.
All players key on the run first except on called blitzes. This makes the D weak to PA but not by much. The secondaries number the WR, TE, and RB 1-3 on their side. CB reads 1, Safety reads 2, OLB reads 3. CB always plays 1 man to man. If 2 goes deep, safety covers him man to man, but if he stays short, safety helps CB over the top. OLB covers the flat and helps with WR and RB screens. MLB cover the middle of the field against crossing routes and slants.
In a pass play, 8 drop into coverage except on called blitzes. In run plays, safeties run downhill into the box, so we get 9 in the box.
It's good against both run and pass, can bring as many as 7 or 8 with various zone blitzes, but has to have fast OLB, CB, and Safeties and is weak against PA.