I was wondering where FS were going with this ability.
It is nice to not have to worry about getting hit while charging your heavy, but from my experience it rarely happens that I get hit during that time because of how devastating such an event is on cata, so I got used to only charging a heavy when feeling sufficiently aware of my surroundings, in combination with preventive dodging.
Seeing how mediocre GK is without the exe sword and how FS went 1 step by adding a block to his exclusive weapon’s heavy charge, why not go all the way and make it activate as fast, or close to as fast as a regular block with that weapon?
That would open up a whole new and fun way of counter gameplay.