First of all, our DLine currently has 2 guys who will have no problems adjusting to the new scheme. Cam Jordan ran a 3-4 in college and is probably better suited for this scheme. Hicks should be able to fill in at either NT or DE when needed. Bunkley may be able to hold his own, but I'm not sure this is a great fit for him. Galette is the odd man out, because this really doesn't fit his style. He is too small to play the DLine, and not agile enough to play OLB.
The LBs are an interesting group. Lofton will fall in to the ILB. Hawthorne can move inside as well. Martez Wilson will fall back to, probably, a more comfortable OLB role. The other OLBs will be Chamberlain and Casillas. Vilma may be restructured, but let's assume he is not. When I look at the successful 3-4 schemes around the league, they all start with outstanding LB play. It seems every year the Steelers or 49ers land a great LB in the draft. If a quality OLB falls to us on draft day, that could be a very good option. I also believe that last years UDFA Braylon Broughton could make an impact in this scheme as a DE/OLB. Keep an eye on him.
The secondary needed an upgrade before the change, and will still need an upgrade after the change. However, I think 2 positions are good. Jenkins, In my opinion is a good FS. Look around the league, he is better than half the other team's options. Harper, while his contract is in need of repair, should flourish in this scheme. People have been calling to make him an OLB for years. Well, if we use a scheme similar to Dick Lebeau in Pittsburgh, the SS is used more like an OLB. He will be close to the line in run support. However, in that scheme, the CBs are required to cover man-to-man over 90% of the time. This poses a problem. We will need help at CB either through the draft or FA.
I think we would benefit more by trading down to get more picks, and necessary pieces to the new scheme. But we can't predict that, so, here it goes, the new mock draft... With the first pick, (with Mingo and Dion Jordan off the board), the New Orleans Saints select, Johnathan Jenkins, NT, Georgia (6'3, 350lbs)
3rd round - Brandon Jenkins, DE/OLB, FSU (6'3, 260lbs)
4th Round - Kyle Long, OT, Oregon (6'7, 310lbs)
5th Round - Baker Steinkuhler, DE, Nebraska (6'6, 290lbs)
6th Round - Brandon Magee, CB, U of Miami (6'0, 190lbs)
7th Round - Stansly Maponga, DE/OLB, TCU (6'2, 265lbs)