doctorbadwolf
Heretic of The Seventh Circle
I agree with your suggestions, except that IMO gritty determination could literally just be “when you fail a d20 test, you can choose to succeed instead, as if you rolled exactly the DC of the test” get rid of indomitable, put this at level 5-ish, with like 2ish uses per short or long rest, and get more at 11, 14, 17, and 20, and call it Heroic Determination because heroic fits the 5e fighter’s fantasy more than gritty does IMO.In brief: (1) decouple Tactical Mind from Second Wind, there is no reason the Fighter should have to give up essential healing in order to get what is, quite literally, merely a suped-up cantrip, and (2) add (after full testing!) a feature like my Gritty Determination (TL;DR: pool = top ability mod + Fighter lv, spend 1:1 to improve any non-Initiative ability check by a total up to your Prof score, stacks with Prof/Expert, must be spent before rolling).
Oh, and I guess (3) for the love of God don't give any of these tools to anyone else. TM should definitely be Fighter 2 or even 3, and Gritty Determination can be 3-5 depending on when they get TM. Simply too deep for anyone to bother multiclassing just to get those tools (especially since my Gritty Determination feature really depends on getting more Fighter levels to be worthwhile.)
Do those things and the Fighter at last has something. It ain't much, but it's honest work. With TM and GD, the Fighter offers soaring highs, as opposed to the Rogue's consistent performance. In a sense, the two swap in combat vs noncombat. Rogues have Reliable Talent and innate Expertise, making their performance floor extremely high, while this hypothetical Fighter can potentially knock an ability check completely out of the park, but may also fall abysmally short. Conversely, Rogues in combat need special conditions to be able to do Big Damage, but Fighters just plug away, making tons of attacks every round and then giving themselves the ability to do it some more now and then.
That's a reasonably interesting mechanical niche for both classes. Fighters are reliable in combat and swingy outside it. Rogues are swingy in combat and reliable outside it.
I’d also give action surge either 1) more punch when used with secondary effects either a) chosen at level 2 like a Holy Order, or b) based on your fighting style choice, 2) more uses sooner eg 2 uses at level 5, 3 at 11, etc, or 3) both 1 and 2.
i guess Heroic Determination could not be any d20 test since TM is already an ability check booster, but tbh having a “use this a lot” and a “save this for dire straits” feature is a good dynamic.