Whilst that would certainly make for a more interesting experience in terms of personal customization and preference, it'd be much more complex. For example, we already know that currently FFXIV:ARR is all about balancing. Everything is balanced in some way. (You can play any dps class as a team and it won't have too much effect overall, as an example) Most of the time what you stated is done in RPG's or primarily single player games. Because it's 100% PVE it doesn't necessarily matter if it's unbalanced. However in an MMO you have to take into account the stats and how it'll effect other players at the same time. Unfortunately I think that this method of being able to wield a Zweihander over a sword and shield if you prefer comes down to how the game mechanics have been built from the start. Perhaps it'd take too long for FFXIV to change to fit this idea as at the moment it's been all about balancing and unfortunately fallen into that cookie-cutter safe zone.