IMO, a top 5 1T would improve the defense quite a bit. I think it maybe the single biggest thing we could do to improve this defense. Adding a guy in the middle who can be a force against the run, would go a long way to helping our LB's stay clean and get to the ball. He would also help our pass rush. Either by shoving the C back into the QB's face, or by by demanding a dbl team to keep him from doing that, which helps free up the 3T and the DE's on their rush. And that would help the secondary make more plays.
I do think the coaching will be better, at least I certainly hope it is. But regardless, it should be more in line with the personal we have and what they know, which should translate into better play all around.