I give it a like for realism and creativity.

BRD in WD = less defense, more power. Automatically cancels when moving.

MCH with GB = less defense, less GCD, less potency on all attacks.

It could work with a drawback that WD needs to be used very expertly or no one is going to use it. Requires quite a bit of precision and timing as it cancels when you move. Also, this will have to nullify the casting time for the song.

I can't say about MCH but if the Gauss barrel doubles the AA instead of removing it, it would see a jump in the long run of a fight but not so in a large, short pulls. Instead, it's near useless in those situations because you want to AOE instead of focusing on a single target.