I have come to propose a new idea for the next PB game.
In our modern world, long swords have been replaced centuries ago by more compact knives that are much easier to store and much easier to handle in close combat. Needless to say, firearms are currently the weapon of choice at longer ranges.
However, in PB2 we see the return of the extended blade in the form of PSI Blades. Though we don't know too much about these weapons, it is apparent that they are easily stored inside a battlesuit, easily manufactured and mass produced at an interstellar level, and extremely effective in combat, being able to even deflect live projectiles.
Which brings us to another recently aged weapon: the bayonet. While it is currently used for ceremonial purposes only, the bayonet was once a very effective and innovative weapon. If, during the wars of the future portrayed by Plazma Burst, we are able to bring back the broadsword of the middle ages, then we can certainly recreate the bayonet.
Although weapon switching is instantaneous in PB2, in PB 2.5/3, there will be a delay when swapping guns. This means that it will take time to switch from a firearm to PSI Blades, and we all know that a few seconds can mean the difference between life or death in hand to hand combat. With the PSI bayonet, however, the soldier can instantly activate an embedded PSI blade in their firearm, effectively converting it into a spear. The PSI bayonet will retain the perks of the original bayonet and improve upon its weaknesses by taking the innovations of the PSI blades in battlesuits, that being its ease to store and handle, and applying it to firearms.
TLDR: PSI Blades except for guns.