Add "passive" equips to the game that allow for more advanced playstyles. Like TF2, these unlocks would give a class passive boosts at the cost of losing a weapon slot, replacing either their primary or secondary. I will attempt to justify them in the order their images are attached.

Medic Stim Injector:
The increased speed boost and passive health would allow Medics to take a less aggressive role, avoiding lethal fights to survive and continue helping their team

Engineer Exoskeleton Legs:
Since Engineer is an exclusively close range class, these would allow him to get into advantageous positions to ambush players that he would normally lose to in a gunfight.

Assault Steel Plates:
The increased damage resistance would allow Assault to tank more damage than usual, letting him become a defensive juggernaut at the cost of being slower and unable to push as hard when on the attack.

Recon Stealth Armor:
This one allows Recon to take full advantage of his gadget loadout, giving him ample ability to set up a sneaky spawn beacons behind enemy lines and cause distractions while his team pushes for the objective.