From my experience playing MNK (since ARR) and SAM, I think outright removing positionals would make the melee classes all kinda flat unless something changed about each class to make them more unique. Positionals were also tied to the reasoning for giving Melee DPS higher potency due to both the angle a mob had to be hit AND the increased danger of being melee.

A quick skill adjustment on True North for longer duration and less recast time is all thats really needed to not invalidate but smooth out the experience for melee and thats if we even really needed an adjustment at all.