[Pyro]

I do like the concept, but in practice, I feel like this would be fairly egegious to melee attackers ?

This is an item that presents a possible issue for both the user and the enemy.

If you trigger a riposte or similar attack on an enemy, they get moved. If an enemy triggers this and ends your turn, you can't hurt them unless you have a movement attack, or you spare the momentum.

Fluer basically overrides it and still allows the attacker to take a second attack. (Though it prevents a third)
Magical damage ignores it (you could spam crescent rook + a physical attack and put yourself out of the range of the person wearing the armor).

It also only applies within one tile. Gigantic weapon users will be eating good for once.

Black Knights can't get indomitable from it. It cannot be given materials like Boulder. Even still, it presents an alternative torso for tanks that isn't just heavy armor with lots of free stats.