Would allowing non-magical martials have physical ability scores of up to 20+tier do anything?
So, the logistically plausible way to do this, I think, would be to give the fighter, rogue, Barbarian, and monk, extra ASI bumps and a higher cap past level 11 or so. The fighter is easiest to do because you just change it’s extra ASI levels to be “you gain aN ASI feat and one other feat of your choice for which you meet the prerequisites” and then for the ones after 11 add, “additionally, your maximum ability score increases by 2”.
The other classes would probably have fewer, with rogue in second place and Barbarian and monk tied for third as the less mundane martials.
An alternative to that would be to give only those classes a flat +1/2/3/etc bump to all d20 tests at certain levels. Again, fighter gets the most, then rogue, then Barbarian and monk.
Maybe the strictly mundane subclasses for each also get a bonus bump at thier 2nd or 3rd subclass slot.
ETA: I wouldn’t restrict it to physical ability scores. Martial doesn’t mean that you charisma, wisdom, and intelligence, can’t be what is most remarkable about you. A Sherlock Holmes character shouldn’t be behind anyone in intelligence, and should definitely be purely non-magical. He would never take the extra time and mental space to learn spellcraft, he didn’t want to know how the solar system works!
