The three fighter feats that feel between them like losing basically half a class out of the game to me are the "hordebreaker" heavy armour master, the "you will fight me" sentinel and the "let someone else try first" polearm master. (Great Weapon Fighter, for all it's a power feat, doesn't change much about what the fighter does).
Just an idea that I'll try if I ever DM a game again:
Create new fighting styles using the different bullet points of said feats, Fighters can swap a Bonus ASI for another fighting style:
Sharpshooter: Ignore the penalty for long range and prone targets with ranged attacks. No penalty to perception in dim light.
Point-blank shot: No Disadvantage with ranged attacks when within 5 ft of an enemy, +1 damage when in normal range.
Quick hands: Can swap weapons as a free action, ignore the loading property.
Cleaving: When you drop an enemy to 0 hp, can make another attack as a bonus action with a heavy or versatile weapon.
Weapon Expertise: You can take a penalty equal to your proficiency bonus to deal double that amount when you make an attack.
Armor finesse: You can add your dexterity bonus to your AC when using medium armors (maximum +3) or heavy armors (maximum +1) and you ignore the Disadvantage on stealth rolls.
Bludgeon Weapon Focus: aka Crusher feat (minus the stat bump)
Piercing Weapon Focus: aka Piercer
Slashing Weapon Focus: aka slasher
Shield-wall: Creatures within 5ft provoke AoO if they make an attack against a target other than you (and that target doesn't have this FS) and you are holding a shield.
Defender: When you hit a creature with an opportunity attack, the creature's speed becomes 0 for the rest of the turn. Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach.
Shield fighter: If you take the Attack action on your turn, you can use a bonus action to try to shove a creature within 5 feet of you with your shield. You can deal 1d6 bludgeoning damage if you successfully shove the target.
Resolute Shield: If you aren't incapacitated, you can add your shield's AC bonus to any Constitution, Dexterity or Strength saving throw you make against a spell or other harmful effect that targets only you.
etc