My intent was to discuss from a design perspective how we could have martial classes that require the same amount of skill and coordination to play as spell casters while still feeling thematically like martial classes. How do we make fighters mechanically engaging while retaining a play environment where most the things they do are at will and spell casters still have daily spell slots, hopefully with individual memorization?
Basically I want to remove the tension between playing a fighter because I like them thematically and playing a psychic warrior or cleric in Third Edition or playing a paladin or cleric in Fifth Edition because they provide the mechanical engagement and challenge I am looking for. Fourth Edition lacked this problem, but fighters did not feel like fighters to me after awhile. So far it looks like Pathfinder Second Edition has solved this problem in one particular way, but I am interested in other possible solutions.
I do think there is some room for a more complex fully at will fighter and would like to see that. Not holding my breath. Just like I do not think we will see a fully competitive true Vancian Wizard like I would also like to see.
I see two basic ways of achieving this:
1) Increase martial options.
Take the suggested additional maneuvers in the DMG and run with them. Add more options in combat beyond grappling and shoving. - Give the fighter bonuses and riders to these maneuvers - many of these may replicate Battlemaster maneuvers so give the Battlemaster even better bonuses and riders.
For example, anyone can shove. Fighter gets to deal their Strength modifier damage on a successful shove and can send the opponent back a distance equivalent to what they rolled on their Str(Athletics) check. Battlemaster has them deal Superiority die as well as Str mod damage, and they deal this damage to anyone they are shoved into.
These maneuvers should inflict conditions that last longer than just the opponent's next move action. There needs to be a tradeoff for losing the additional damage of a normal attack.
2) Leave the Fighter alone. Create a new class based around maneuvers like the Warblade of the Tome of Battle. As Tony Vargas has noted, the Fighter base class has too much combat power in its multiple attacks, and this limits the scope of giving additional capabilities. A new class could be designed so that their DPR was still a little less than a Fighter's, but their maneuvers could give allies advantages, inflict conditions on opponents, and give them out of combat capabilities.
Hmmm
What about giving them something between a daily and an at will?
Like a number of special strikes and extreme feats of physicality scaled to number of physical attacker hd per day? Including but not limited to dealing a portion of damage as messy physical ability damage for periods of time?
Or temporary feats of crazy athleticism also using a limit of uses per day scaled to class hd?
Or a different way of doing the latter would be being able to dedicate energy to continuous feats of physicality of a specific type per class hd persisted tgrpughout the day.
Example: level 4 fighter dedicates 2 hd of his toughness to opperating normally in spite of a currently active physically debilitating disease all day 1 hd to carrying heavy load all day and moving as if with a light load (but ungainly objects still applying to restricted movement where space limitations would cause a tight squeeze) and 1 hd dedicated to convert 1 point of damage from any damage die roles rolling above average (for the die type) to a physical ability damage point all day long.
All such hd daily dedications would need to be charted so that it was standardized to have a list of the number of hd necessary for each.
The Extreme Explorer Barbarian class in the Eberron supplement has something similar: they can spend Hit Dice to add to some rolls (and take some damage).
A Fighter variant that spends HD to activate maneuvers would be possible, but I do not think that it is a good mechanic. - I don't like any "Hurt yourself to do X" mechanics since they move the burden of sustaining your health and class abilities onto another character (the healer).
The Fighter already has a couple of limited-use abilities that mark it as the "Heroically push beyond their limits" class: Second Wind and Action surge. I would recommend leaving Second Wind as-is.
Action Surge could be given more capabilities. For example:
"As part of making a Str, Dex, or Con ability check or saving throw, you may spend an Action Surge. When you do so, you may add all of your Str, Dex and Con modifiers to the roll, rather than just the one normally applicable."
This would give a potential boost to skill use and a little more resilience against status effects in combat, without adding a big power boost compared to other classes. A well-rounded fighter might get a better bonus than the Rogue's expertise, but only for a limited amount of rolls. I'd actually allow it to be used for mental ability checks and saves (adding Int, Wis and Cha modifiers together.)
However the issue we run into is that Action Surge is too powerful for an ability like that. As it is, any ability that involves spending an Action surge is competing against taking the extra attacks in combat. Giving more action surges boosts the Fighter's nova, which is not something needing shoring up. More action surges, but each only granting an extra attack might work, but may not be popular.