I think it’d be a cool idea to have a Guard Kasarkin (the original, pre-Scion lore) class. It’d fit the game lore a bit better too since Kasarkin where selected in part from the veteran guard, while Scion are genetically altered and raised from birth to be between a guard and space marine.
The lore of a Kasarkin Guardsman from Cadia (already in the game lore wise) who maybe failed his critical mission task, possibly being the sole survivor and is being punished, but taken by the Inquisition for their combat skills is a super cool lore idea as another one of the rejects.
I REALLLYYYY hope they put this in the game. Hell even if he was a free (or like $5) DLC character later on (i think its too close to launch to add a whole new class) is a great way to expand playability.
My version that i think is better than the OP for lore and story purposed of the game:
Unique weapon- Hotshot vollygun:
I think his unique weapon should be the hotshot vollygun, while his base class revolves around the progression from regular lasgun, to regular hot-shot lasguns. The melta gun is lore wise even rarer than plasma, and is mostly a anti-tank weapon, and since this game has no armored vehicles, and focuses on strategies and teamwork to deal with things like bulwark enemies who can stop frontal attacks, I don’t think its as cool or good weapon to add since it would make that enemy type completely pointless.
- A rapid fire variant of a hotshot lasgun. Higher rate of fire, automatic, but has no precision sights since its a lot heavier to hold (cant shoulder, its mostly hip fire). Requires no reload (just like hotshots) since the entire backpack is the weapons ammunition supply. Can overheat and require cooldown time (10 seconds?) if you sustain the rate of fire for more than like 20 seconds straight.
Unique Grenade - Krak:
I think his grenade should be krak type, which is a mass produced grenade anti-armor grenade for more elite guard troops (like Kasirkins), but not as powerful as melta.
- It should have very low blast radius, and explode upon impact since its a type of shaped charge. Its direct impact damage should be very high, but anything past like 2 feet should be unaffected (maybe a slight stagger, but no damage). 4 grenades just like veteran class.
Ability - Overcharge:
A lot of elite units of the guard, while being better equipped, know that they get sent into some of the worse places imaginable against the strongest opponents guard can feasibly handle. Because of this, sometimes doing modifications (sanctioned or field modified) to their weapons to output more power, at the cost of increased wear and total ammunition used is done. One case of this is “overcharged” settings for las weapons. This can be done by modifying the power packs that output more power than normal into lasweapons, or by modifying the weapon to drain a normal power pack more aggressively. This increases overall damage, but it reduces the amount of shots per pack, meaning the troops have to either carry more, or make sure to hit more often.
- How it would work → When this ability is activated, the weapon is switched to “high power” mode and it uses 40% more energy per shot, for 25% more damage, and 10% better armor piercing. In addition, it shows the fire rate of the weapon by 15% since the gun needs more time to charge between shots to get the full “overcharged” shot power.
- This would mean the player can choose normal fire mode, or when they really have a heavy target, they can choose a higher damage and penetration mode at the cost of rate of fire and ammo consumption.
Special melee weapon - Power fist:
Since Hotshot lazguns (and vollyguns) require specialized power backpacks, I think a cool melee weapon that could be added is the Power fist. The reason why is Imperial Guard power fists require a external power source (for the mass produced variants) to operate, normally carried on the troops back. Since the Kasirkin class would already have this backpack to power their hotshot weapons, it’d be a cool class specific melee weapon that can be added.
- How it works → Hard as hell hitting (lore wise they over doubles a humans natural strength level depending on the person).
– It has a quick attack that is a side swipe punch that is good for hordes, doing more damage but its slower than a sword.
– Its long hold attack (slow attack) is a angled uppercut. Higher damage, chance of knockdown or stumble, but less wide range than regular side swipe hit.
– It can block by just raising the arm up and using it to block the attack (no parry).
– Its special attack mode is a powered piercing punch. You activate it, and you have a few seconds to hit the target before it powers off (kind’a like the chain sword). It does a lot of damage and penetration, and has heavy knockdown/stun change, but can only hit the direct target your aiming at (unlike the other attacks).
Hope ya’ll consider this idea, and if fatshark, you use this idea, I want a free code for this class if your making it not a free DLC 
