The following homebrew adds a modern option to the Fighter class in 5E TTRPGs. All of the core Fighter class abilities can stay rules as written; see the official 5E System Reference Document (SRD v5) for details. Note: This subclass has not yet gone through playtesting.
Spacefleet Officer
Trained in the finest academies and tempered by the dangers of deep space, you are the backbone of any exploratory or defensive crew. You balance martial expertise with scientific awareness and command readiness. Whether you’re leading an exploratory team into an alien ruin or taking the conn in battle, your mission is to protect your crew and uphold the ideals of your interstellar nation.
Level 3: Command Discipline
Your training blends combat precision with leadership and crisis management. You gain the following benefits:
Command Presence. When you take the Attack action, you can forgo one of your attacks to issue an order to an ally who can hear or see you within 30 feet. That ally can immediately use their Reaction to take one of the following actions:
* Make one weapon attack.
* Move up to half their speed without provoking opportunity attacks.
* Take the Help action targeting a creature within 5 feet of them.
You can use this feature a number of times equal to your proficiency bonus per Long Rest.
Analytical Combatant. You gain proficiency in either Insight, Investigation, or any one technological tool. When you make a check using that proficiency in the middle of combat or a tactical situation, you can add your Wisdom modifier in addition to the normal ability modifier.
Level 3: Beam Weapon Training
You’re trained to use energy-based ranged weapons with precision. When wielding a laser, blaster, or other energy beam precision ranged weapon:
* You can use Dexterity or Intelligence for attack and damage rolls (your choice).
* You ignore half cover when attacking a target you can see through sensors or readouts (such as helmet HUDs, tricorders, or starship scanners).
When you roll a natural 20 with an energy weapon, you may choose to stun the target instead of dealing extra damage; the creature must make a Constitution saving throw (DC 8 + your proficiency bonus + your attack modifier) or be Incapacitated until the end of its next turn.
Level 7: Exploratory Team Tactics
You’ve led or served on countless missions and can adapt your approach instantly. At the start of your turn, choose one Mission Protocol to activate for 1 minute (no action required). You can change protocols as a Bonus Action.
Security Protocol. You and allies within 10 feet gain +1 AC while you remain conscious.
Science Protocol. You and allies within 10 feet gain advantage on Intelligence (Investigation), Wisdom (Perception), and Wisdom (Insight) checks.
Engineering Protocol. When you or an ally within 10 feet makes an ability check to repair, hack, or stabilize a device or structure, they can add your proficiency bonus to the roll.
You can use this feature a number of times equal to your proficiency bonus per Long Rest.
Level 10: Starship Coordination
You are trained to fight as part of a bridge crew or tactical team. While aboard a spaceship, starship, shuttle, or other crewed vehicle, you can use your Action to assist its operation in the following ways:
Tactical Oversight. Add your proficiency bonus to the ship’s next weapon attack or defense roll before the end of your next turn.
Damage Control. Direct repairs to one damaged system, restoring a number of hit points equal to 2 × your Fighter level to the ship’s hull or a subsystem.
Pilot Assist. Grant advantage to the next Piloting check made by a creature at the helm.
Additionally, while aboard any crewed vessel, your presence inspires confidence: All friendly crew gain temporary hit points equal to your Wisdom modifier when combat begins (minimum 1).
Level 15: The Mission Directive
Your professionalism and restraint are legendary. You have advantage on saving throws against being Charmed or Frightened, and when you or an ally within 30 feet fails a saving throw, you can use your Reaction to allow them to reroll it. They must use the new roll.
You can use this feature a number of times equal to your Charisma modifier per Long Rest (minimum 1).
Level 18: Engage!
Your mastery of command and timing turns every battle into choreography. When combat begins, you can immediately issue a tactical directive as part of rolling Initiative. Choose up to three allies who can see or hear you. Each of them can take one of the following options immediately (no action required):
* Move up to half their speed.
* Draw or stow one weapon or item.
* Make one weapon attack.
In addition, for the first round of combat, you and those allies add your Charisma modifier to all attack rolls and saving throws.
Once you use this feature, you cannot do so again until you finish a Long Rest.