Regarding what I'd do with the lines and draft:
Defense. Buffalo's zone heavy 4-2-5 defense has the same strengths and weaknesses as the Tampa 2. To run this style of defense, the GM needs to pour resources into the defensive line. Linebackers and defensive backs can be trained up to starters and contributors due to the zone heavy nature of the defense.
For this defense to be effective, the defense has to be able to both read and react (the base) and attack (the adjustment). To do both effectively, you either need a ton of stars on the line (think 2000s Tampa Bay with Sapp, Rice, McFarland) or you need waves (think 1990s Dallas rotating 7 different defensive linemen into the mix). Based on what Buffalo has already, I'd advocate for a Dallas style defense which has a run group and a pass group.
The Bills will have Rousseau, Epenesa, and Miller at end, and Oliver, Jones, and Carter at tackle. Rousseau is going to be a player for the Bills long term. Epenesa is signed through the end of next season. Miller is a potential cap cut at the end of the season. The Bills have a 2-year solid plan but could use another rotational starter.
At tackle, Oliver is signed long term. Carter is a rookie, and Jones is signed through the end of next season. Buffalo could use reinforcement at nose tackle.
Offensive. The Bills are in a good spot at offensive tackle with Dawkins and Brown signed long term. McGovern and Edwards are signed through the end of next season. Torrence is still on his rookie contract. Nearly all the backups are later round developmental players, with the exception of Van Pran-Granger, who fell to the 5th round in the 2024 draft. Grable and Clayton are the only other offensive linemen on the roster past this season.
Some teams like to wait until the need for a player arises, and then acquire help. I don't advocate for that on the offensive line. Linemen can be developed, and with a coach like Kromer, I'd rather give him more talent than later round projects. I think Buffalo should use some higher end picks on offensive linemen who can be developed.
Off-season plan. I wouldn't count too heavily on free agency. The Bills are in season 2 of version 2 of the Allen Bills. Beane needs to keep cap space, and he's got both lines intact for next season. I recommend taking a year to reset line depth so there isn't a drop off.
The defense needs waves to attack along the defensive front. I'd look at a defensive end opposite Rousseau for the long term, and a big bodied nose tackle.
The offensive line could use more talent to back fill Edwards and McGovern when they depart. Getting some high quality players a year to develop behind starters, especially with Kromer as the line coach, could deliver incredible results. We're seeing what a good line can do to help Allen and the run game.
An Illustrative Draft Plan. This plan isn't lock step, and it's way early. It's meant to illustrate what type of draft it would take to make a reinforcement plan work. I'm using PFF's big board.
Round 1: Jack Sawyer DE, Ohio State. Sawyer is a physical end who would book end Rousseau.
Round 2 (trade up): Dontay Corleone DT, Cincinnati. One of two high end NTs available in the draft. Buffalo trades up in the 2nd round using a 4th to make this pick.
Round 2: Jonah Monheim OL, USC. Monheim played 2022 at RG and RT, 2023 at LT, and 2024 at center. He's a high-end talent who can play anywhere on the line. He's a little like Cody Mauch from the 2023 draft.
Round 3: Wyatt Milum OT, West Virginia. Athletic, 3-year starter at WVU.
Round 4: Nick Martin LB, Oklahoma State. McDermott style fast linebacker.
Round 4: Nick Emmanwori S, South Carolina. Siran Neal style player.
Round 5: Nazir Stackhouse DT, Georgia. NT type who I'd pick earlier if needed.
Round 6: Raheim Sanders RB, South Carolina. Power runner who could round out the Bills running back group.
Round 7: Bryce Foster C, Kansas. Texas A&M transfer who has Creed Humphries level athleticism which has not translated to the field. Developmental pick.
How this effects the lines:
Defense. Babich could build waves. Rousseau, Epenesa, Miller, Solomon, and Sawyer aren't pigeonholed into pass or run down players, but now the depth supports that type of rotation. Jones, Corleone, and Stackhouse can be rotated, with Corleone eating run downs and saving Jones for pass downs. Oliver and Carter are the 3T DTs. Babich could even package a run down package of Jones and Corleone, and bring in Oliver and Carter on run downs. There are options and a lot of high end players and prospects.
Offense. Dawkins - Edwards - McGovern - Torrence - Brown remains an exceptional starting group. That group is backed up by Milum and Grable at OT and Monheim and Van Pran-Granger at C/G. After next season, Edwards and McGovern might not be on the team, and Kromer would have options of who to start.
That's how I'd keep the lines strong and improve them to match up better with teams like Baltimore.