since we're talking tweaks to Fighters, might as well share this here...
I’ve been mulling over this concept for a while now, Advanced Fighting Styles (or Secret Fighting Styles?) that are linked to skills. Either you need proficiency in a skill to gain them or you learn that skill as part of the training for that style. I’m not sure where to slot this idea: as a subclass feature or as an alternate rule or a bonus?
Here’s what I got so far :
Dancing Mantis
Skill: Performance
If you inflict slashing damage to a creature, that creature cannot make opportunity Attacks against you until the end of the turn.
Dazzling Unicorn
Skill: Arcana
Once per turn, while you are holding a weapon and have a free hand, you can spend a bonus action to enchant your weapon until the end of your next turn, or until you drop the weapon. While enchanted, your weapon inflicts magical Radiant damage. Starting at level 11, add your Intelligence modifier to the damage dealt by your enchanted weapon.
Hunting Eagle
Skill: Perception
Once per turn, when attacking with a ranged weapon while you do not have advantage or disadvantage, you can choose to attack with disadvantage. If that attack hits, it is considered a critical hit.
Patient Turtle
Skill: Insight
If you do not move on your turn, or you use Second Wind, the next attack made against you before the start of your next turn is made at a disadvantage.
Prowling Wolf
Skill: Nature
When attacking with a simple weapon, you gain a +2 to the attack roll if an ally you can see is within 5 feet of the target.
Rushing Rhino
Skill: Athletics
You can attempt to shove creatures 2 sizes larger than you rather than just 1.
Steadfast Bear
Skill: Intimidate
You have advantage on all saving throws against the Frightened condition. You add your Strength modifier to any ability check that uses your proficiency in the Intimidate skill.
Striking Cobra
Skill: Sleight of hand
You have advantage on attacks made using a Light weapon you drew as part of your Attack action. You can apply poison to a Light weapon as a bonus action.
Tumbling Monkey
Skill: Acrobatic
If you inflict damage to a creature using a weapon with the reach property, or a quarterstaff held in two hands, you can move 5 feet as a free action. This movement does not count toward your maximum movement speed for the turn.
Unstoppable Boar
Skill: Survival
Whenever you take damage, you gain temporary hit points equal to your Constitution modifier.
Feel free to suggest concepts that could work for the missing skills: Animal Handling, Deception, History, Investigation, Medicine (buff to your Second Wind?), Persuasion, Religion, Stealth.