Stamina

Each character has a resource called Stamina.  You have a number of Stamina points equal to 1+Your Constitution modifier (minimum 1.).  Certain actions described below require stamina to be performed.  Whenever you use a stamina point, you regain it at the end of your next turn.

Your maximum stamina is reduced by 1 for each level of exhaustion you have (minimum 0).

Universal Stamina Actions:
Dodgeroll - As a reaction whenever you are hit by an attack or are targeted by an ability that forces you to make a Dexterity saving throw, you can spend 1 stamina point to make a dodgeroll.  If the triggering effect is an attack, the attacker must reroll their attack and take the lower result.  If the triggering effect is an area of effect ability, you gain advantage on the saving throw.  In either case, after the attack or effect is resolved, you can move up to half your speed without provoking opportunity attacks.

Sprint - You can spend 1 stamina point to increase your speed by 15 ft until the end of the turn, requiring no action.  You can use this ability outside of your own turn.

Heavy Attack - You can spend 1 stamina point whenever you make a weapon attack to turn it into a heavy attack.  You forgo your proficiency bonus to the attack roll.  If the attack hits, you deal bonus damage equal to your proficiency bonus or twice as much if you made the attack with a melee weapon held in two hands.  You cannot combine this with light attack.

Light Attack - You can spend 1 stamina point whenever you make a weapon attack to instead make two light attacks.  You forgo your ability modifier to damage rolls if the attacks hit.  You cannot combine this with heavy attack.

Precise Attack - You can spend 1 stamina point whenever you make a weapon attack to attack your opponents weak points.  You have disadvantage on the attack roll but if the attack hits, the attack is a critical hit.  Alternatively, you can make a called shot, imposing disadvantage on your attack but adding a bonus effect if you hit.

Head - Target must make a Constitution saving throw, the DC of which is equal to 5+half the damage taken, or be stunned until the end of your next turn.
Arms - Target must make a Strength or Dexterity saving throw, the DC of which is equal to 5+half the damage taken, or drop whatever is in their hands and have disadvantage on attack rolls until the end of your next turn.
Legs - Target must make a Strength saving throw, the DC of which is equal to 5+half the damage taken, or have their speed reduced by half until the end of your next turn.

Fighting Style Locked

Cleave Attack (unlocked from Great Weapon Fighting) - Whenever you hit a creature with a melee weapon attack, you can spend 1 stamina point to cleave into a nearby target.  Choose a creature within your reach and within 5 ft of the creature you hit.  If the initial attack roll would hit the second target, they take half the damage you dealt to the first target.

Shotthrough (unlocked through Archery) - Whenever you hit a creature within a ranged weapon attack, you can spend 1 stamina point to have the attack pierce through the target.  Choose a creature within range of your weapon and in a line from where you attacked the initial target from.  If the initial attack roll would hit the second target, they take half the damage you dealt to the first target.

Block (unlocked through protection) - *Requires a shield* Whenever you or another creature within reach of you is targeted by an attack or by an effect that requires a Dexterity saving throw, you can spend 1 stamina point to impose disadvantage on the attack or the give the targeted creature advantage on the saving throw.  If the creature still takes damage from the triggering effect, you reduce the damage by an amount equal to your shield bonus + your proficiency modifier.

Dueling (unlocked through dueling) - *Requires a finesse weapon* Whenever you are within 5 feet of a creature and no other creatures are within 5 feet of you, you can spend 1 stamina point to gain advantage on all attack rolls made with finesse weapons this turn against that creature.

Deep Wounds (unlocked through two weapon fighting) - Whenever you hit a creature with at least two weapon attacks in a turn, you can spend 1 stamina point to deepen their wound.  The target takes your weapons damage dice in bonus damage for every 2 attacks you land.

Intended with the following changes -
Defense fighting style removed

Engaging in Two Weapon Fighting adds your ability modifier to the second attack.

Two Weapon Fighting now reads: "Engaging in two weapon fighting no longer requires a bonus action for you."

Protection now reads: "Whenever you end your turn, you can choose one creature within your reach as your protection target.  That creature gains a bonus to their armor class equal to your shield bonus until the start of your next turn."

Likely some changes or outright removal of battlemaster, implementation of some of the maneuvers as stamina abilities (?)

Barbarian gets a fighting style, probably at level 2 or something