Would love to go for Stephon Gilmore and Justin Simmons.
At CB right now, we have Christian Gonzalez, Jonathan Jones, Alex Austin, Marcus Jones, Marco Wilson, Isiah Bolden. Gonzalez showed good promise as a rookie and is an unquestioned started on the outside. Jon Jones has been fine outside but is best in the slot. Alex Austin played well down the stretch, but would be better served as the depth option at outside CB vs. starter, IMO. Marcus Jones showed some flashes on defense, but again is probably a better depth option than starter. Marco Wilson and Bolden are camp competition types right now, with some promise. Add Gilmore to the mix as a starter opposite Gonzalez and also a mentor. That pushes Jon Jones back into the slot where he's best. Austin and Marcus Jones provide great depth on the outside (Austin) and inside (Jones). Marco Wilson or Bolden have an opportunity to make the team in a 6th CB role depending on final numbers.
At FS, we don't have a center field type. Justin Simmons excels in that role. You can keep running the 3-safety looks with Dugger and Peppers, using one of them as a LB and playing lots of dime like we have in the past. Mapu rotating in too I guess, but more a depth option than key contributor for as long as both Dugger and Peppers are here. Simmons plugs the whole in cover 1 schemes and adds another good vet.
Both Gilmore and Simmons are respected locker room guys so they add character and leadership too, along with filling in on-field areas of weakness on an overall solid unit.