It's actually a call back to the way Fists used to work originally, believe it or not! They all used to simply drain MP in the exact same way Foe Requiem did - trade MP for a buff.
That said, it wouldn't be true MP management. Think of it like FoF having the MP bar ticking down instead of having a traditional buff timer ticking down (except it only ticks down when you use a GCD action). FoW would be used directly after and would refill the MP bar (I accidentally deleted that part) through normal gameplay in lieu of having a recast timer for the FoF buff - it would fill slightly faster with Tornado Kick usage when it's learned in lieu of having a traditional recast timer reduction trait. It would sort of echo PLD's MP management in a world where they only had 1 spell that used MP. More symbolic than anything and requiring about as much thought as MCH's Queen usage.