Making shift grip an action that can be performed with a move would solve it.
Extra reaction with training too.
Or, to the point of making the greatsword too powerful, make 2 handed weapons make you sluggish(1) or something when held in one hand.
I’m still stuck on the idea that failing on offense (an attack) means you fail to progress. Failing on defense (saves) means bad things happen. But in skills failing on offense is bad, and they are all offense in my current mental paradigm.
Reading the blogs I was really keen on making a dual wielding Barbarian cause Double Slice made it look really cool, only to be saddened to find out they don't have access to the Double Slice feat. And lots of the classes were in that predicament.
But... But... Fighter Dedication feat! Suddenly a whole new world opens up.
So one feat that gets you nothing but the honour to be allowed to take a cool feat in 2 more levels?
I kinda had an idea that you should handle fighting similar to spell casting. You have different skills that represent the training and style. Brutality, Martial, Finesse, Thrown, Ranged, Unarmed maybe.
Barbarians would get Brutality, Paladins Martial, Rangers pick one, Fighters pick one or two initially and more as class features/feats.
You could then tie weapon feats to the style, rather than class. Cleave requires trained in Brutality, Point-Blank a Ranged feat.