That doesn't answer the question really.
Okay.
So you hit an enemy from 100 ft away, and then if they move on their turn, you get to shoot them two more times with advantage as a reaction. That is incredibly powerful for 10th level, and also raises a question... what is the point of being a melee character?
On of the things melee characters can do, is help control the battlefield by preventing enemy movement. This ability is FAR better, and imagine what happens if the fighter has this and took push mastery? You are 10 ft away, hit the enemy, pushing them back 15 ft. On the enemies turn they charge you to engage in melee, you hit them two more times with advantage, moving them back to 20 ft away. You are, quite literally, untouchable.
Now, I grant, you can solve this problem the same way you solve PAM+Sentinel, send more enemies. However, this is a rather extreme combination of abilities, and now you need to match this power with new options for polearms, heavy weapons, sword and board, and dual light weapons. And two attacks at range with advantage as a reaction is going to be HARD to match the power of. And then you need something even stronger for "weapon perfection"
Suppression is an action. You don't get attack unless the target moves.
You think I haven't designed other Grandmastery Feats
Grandmastery of the Axe
Prerequisite: Level 10
+1 STR or CON
When you attack with a battleaxe, handaxe, or greataxe you have mastery with, you can treat them as if they have both the Cleave and Topple mastery.
When you attack with a battleaxe, handaxe, or greataxe you have mastery and use the Cleave mastery, you make an attack a third and 4th creature within 5 ft of the first.
Grandmastery of the Hammer
Prerequisite: Level 10
+1 STR or CON
When you attack with a light hammer, warhammer, or maul you have mastery with, you can treat them as if they have both the Push and Topple mastery
Creatures have disadvantage on the Constitution saving throw from a light hammer, warhammer, or maul you wield with the Topple mastery property
Grandmastery of the Spear
Prerequisite: Level 10
+1 STR or DEX
When you attack with a javelin, pike, lance or spear you have mastery with, you can treat them as if they have both the Push and Sap mastery
When you attack with a javelin, pike, lance or spear you have mastery with and the Push Mastery property, you can push them additional feet equal to your Strength score and there is no size limitation.
Grandmastery of the Sword
Prerequisite: Level 10
+1 STR or DEX
When you take the Dodge action while wielding a longsword, greatsword, rapier, or scimitar you have mastery with, you may roll an attack roll and use it as your AC as long as you are wielding these weapons and not incapacitated
When you attack with a longsword, greatsword, rapier, or scimitar you have mastery with, you can treat them as if they have both the Gra
ze and Sap mastery