Basically the idea is to give every class a single, additional slot in which they can slot one of a handful of exclusive abilities. Some of these would help shore up a class' weaknesses (like letting gunners repair their guns faster than an engie could), improve on their strengths, allow for specialization, and/or just add a bit of extra variety to the game.
Here's a few ideas example ideas, I won't give exact numbers since I don't have a full comprehension of the specifics of this game yet, but here they are.
Engineer:
Speedy Service - Boosts an Engineer's movement speed, jump height, and ladder climb speeds to get to ship components in need faster.
Deft hands - Reduces cooldown time on repair tools for faster repairs.
Tinkerer - Improves the buffs given by the Buff Hammer and extends the protection period of the Chemical Spray Extinguisher. Sort of making this a "buff specialist".
Gunner:
"Don't Touch My Gun!" - Increases repair power on weapons while reducing cool down on fixing them. Also grants short period of increased damage with reduced recoil when you repair a gun from broken.
Point Blank Shooter - Grants bonus damage as an enemy ship is, also increases the arc you can swivel your gun by a few degrees more in all directions.
Sniper shooter - Grants bonus damage the further away an enemy ship is, also gain a small, additional bonus to attacking engines.
Pilot:
Dare Devil - Increases benefits gained from piloting tools, especially self-damaging ones
"Play it safe" - Reduces penalties received from piloting tools, especially self-damaging ones
"Just a dent" - increases the amount of HP ship components can be repaired for.
Well, these are just a rough idea. So what do you guys think overall?