People are talking about classes, but a selectable 4th slot would be a simple way to have a specialized tactic to suit current needs.
Selecting a forth slot would be much like selecting a weapon, but it would come after weapon selection.
A few suggestions are listed below:
3) Medikit - restore a margin of health to either you or allies, right click to restore own health, left click to restore ally health when aimed at them in a spades reach. Up to 3 uses.
2) Munitions kit - restore ammunition of yourself or allies, used like the medikit, right click to restore 30% of of the weapons maximum [when you spawn] that you hold, left click to restore 30% of an allies weapon maximum within a spades reach. Up to 3 uses.
Rifle gains 15 rounds.
SMG gains 40 rounds.
Shotgun gains 14 shells.
1) Grenades - The current default 4th slot, 3 grenades, three uses. Can be used to disperse enemies in a certain area. Left click to prime grenade, release to throw. A right click action could be added, a roll of the grenade, hold right click to prime, release to roll. Rolling the grenade is most effective on flat ground, or a slope.
Three options to choose, much like our three weapons.
Discussion begins.