I don't hate it , but it doesn't fit this team or it's personnel . I think this team could easily make the switch back to the 4-3 and only need to add a couple of parts during the draft/free-agency .
They would probably need another pass rush DE to spell Ware and Spencer . You could probably bring Ellis in with his hand on the ground occasionaly , but I'd hate to count on him . I think Bradie , Bobby , Kevin , and Zach would all perform better in a 4-3 , but you would probably need to bring in an additional OLB . That's pretty much it . D-line would be fine as well as the secondary .
Now you stay the 3-4 . You have to go get a NT , might need a DE to replace Canty or Spears depending , and a MLB who can actually get off blocks , maybe two . That's an awful lot to put into a defense that's already full of first day picks .
The biggest issue would be finding a coach who could run that 4-3 , and make the conversion . Still , the coaching candidates broaden when you go 4-3 , and names like Singletary , Harbaugh , Spagnuolo , and Ryan paired with Garrett begin to sound pretty good .