Homebrew

Traits

Tech aptitude. Advantage on Saving Throws against Magic.
Line infantry tactics. When 2 or more allied soldiers are nearby they have Advantage on Saving Throws.

Actions

Multi Attack. The sergeant makes two attacks and uses a command ability.   Revolver (bullet). To hit: 1d20+9 , on hit 2d8+7 Piercing or Bludgeoning. Fatal Shot: on Critical Hit, 1d10+17 instead.
1/day Revolver (Tracer). To hit: 1d20+9 , on hit 2d8+7 Piercing or Bludgeoning. Fatal Shot: on Critical Hit, 1d10+17 instead. Tracer. It leaves a lit trail to the target. The next attack against the creature is with Advantage.   Scattershot (Pellet Shot). Range 15 ft. Cone, centered on self, Dexterity Saving Throw DC14, on failure 1d10+1 Piercing damage, Fatal Shot (when creature rolls natural 1 or fails the Saving Throw by 10 points or more, add 12 additional points of damage), bludgeoning or piercing damage. Roll the damage once and apply it to each creature that failed the Saving Throw.
1/day Scattershot (Dragon's Breath) In a 100 ft, 5 ft line centered on yourself all creatures must make a Dexterity Saving Throw, on failure the creature takes 8d6 Fire damage and on successful save half damage.

Bonus Actions

Fire at Will! Use your Bonus Action or Reaction to choose an ally within a 30 ft. radius that can see and hear you to allow them to use their Reaction to make a weapon attack. On a successful hit, they add your Charisma Modifier to the damage roll.   Move! You can use your Bonus Attack or Reaction to allow an ally within 30 ft. radius that can see and hear you to move up to half their movement speed.