All of my ideas would be for rank 5 and above.
Universal
Marksman - Improves accuracy and stability of Primary weapon by 25% when using ADS
Gunslinger - Reduces weapon switching time by 40%
Battle Tested - Improves health regeneration by 30% (Coupled with Battle Hardened, this means you’ll spend less time hiding after taking damage and more time fighting)
Soldier
Concussion Grenade - Flashbang grenade that does damage on impact. (The damage would be 20% less then the standard grenade)
Clip Belt - Increases a soldier’s reload speed by 25%. (This is on top of the reload speed of whatever weapons are in your load out, so Soldier can reload incredibly fast, since they’re supposed to be the guys leading the charge.)
Run & Gun - Improves stability and accuracy by 25% while hip firing. (Coupled with the Clip Belt, this will make Soldiers offensive powerhouses, as they’re supposed to be.)
Engineer
Extra Turret - Same as Extra mine, this will give you the ability to deploy 2 turrets. (The catch would be the 2nd turret will always be weaker the the 1st. So if you deploy a Gatling Turret, your 2nd deployed turret will always be a medium.)
Control Turret - Allows Engineers to manually control their own turrets. (Operatives can do it after hacking it, so why can Engis do it outright?)
Proximity mine - A mine that detonates when an enemy gets withing a 5 meter radius of it.
Medic
Self Adrenaline, Metabolism & Speed Boost - Allows you the ability to give yourself either of the boost you can give your team, but only when you have it equipped. (You’d simply select it as if you were going to buff a team mate, but instead apply it to yourself when not looking at a team mate.)
Pheonix Grenade - Same effect as the Lazurus grenade, but revived team mates will not only have full health upon reviving, but an adrenaline boost as well. (There’d naturally be an EXTREMELY long cool down between uses, so you’d want to use this one wisely, preferably as a last resort when pushing into an objective or defending it and a number of your squad mates are downed.)
Mega Serum - A special serum that when injected, grants team mates increased agility and speed for a set limit of time. (Heavies will be able to move as fast as Mediums, and perform Medium SMART moves, Mediums will move as fast as Lights and be able to do Light SMART moves, and Lights will move at incredible speed and be able to DOUBLE wall hop.)
Operatives
Extra Caltrop Grenade - Allows you to throw two Caltrop grenades instead of one.
Tracking Device - A device that can be placed on an enemy that gives the Operative unlimited intel on said enemy. His health, current buffs, ammo and location on the map. It can be only be removed by an Engineer or an Operative. (It’d be used like the Sticky Bomb.)
Master Of Disguise - The next step up for the Disguise ability. With it, an Operative can do all actions without breaking disguise unless spotted by the enemy he’s disguised as or another Operative. (You’d break disguise by putting your crosshair on an enemy and holding the prompt button as if to give a buff. This would be the greatest tool for a high level Op, as they’d be able to do some SERIOUS damage if they’re good enough to remain undetected.)