I,'ve been testing with one of my players that plays a warrior from The Promised Land. We replaced Action Surge with a flat bonus equal to the proficiency bonus at each warrior level and a critical threat increase. We named it Weapon Training. The damage output is about the same (or better) compared to Action Surge in a combat that lasts 5 rounds of more.
Aside playing the story, my player enjoyed the change and he had fun with his extra critical scores.
# You can use it every turn and don't need to hold you super power because you have only one use.
# You don't need to rely on Short Rest to recharge.
# Fighters are experts with weapon fighting, so it fits well.
# Players like more damage.*
# Players like when they score a critical.*
# If you have a generous Gamemaster that gives the group enough Short Rests, Action Surge have a good fun factor for one turn (two at 17th following the fighter progression).
# Players like bursts in damage*
* This an assumption but I think is general enough.
Weapon Training. At 1st level, you can select two group of weapons, as noted below. Whenever you attack with a weapon from these group, you gain a bonus to damage rolls as shown in the Fighter table.
Additionally, at 2rd level, your weapon attacks score a critical hit on a roll of 19 or 20.
At 17th level, your weapon attacks score a critical hit on a roll of 18-20.*
* following the fighter progression.
Axes. battleaxe, greataxe, handaxe, and war pick.
Blades, Heavy. greatsword, longsword, and scimitar.
Blades, Light. dagger, rapier, short sword, and sickle.
Bows. longbow, and shortbow.
Crossbows. hand, heavy, and light crossbows.
Firearms. all firearms.
Flails. flail, morningstar, and whip.
Hammers. club, greatclub, light hammer, mace, maul, and warhammer.
Polearms. glaive, halberd, pike, and quarterstaff.
Spears. javelin, lance, spear, and trident.
Thrown. blowgun, dagger, dart, net, sling.
Siege Engines. all siege engines.