So there are only 12 weapons? That seems low for an rpg.
Well, why don't we list the 'melee' weapons first off that we have seen in promo material before the game's even out?
Saw cleaver, axe, hammer, whip, giant scythe, dual daggers, and fist weapons.
That's already 7 melee weapons, but each of these has a 'second form' that plays so differently it might as well be a new weapon. The cleaver retracts into a sort of shortrange axe, the regular looking axe turns into a long polearm weapon, the hammer turns into a dual wield set of a sword and smaller hammer with its own moveset, the whip is also a cane sword, the scythe is also a shortsword once you join the pole and the blade, the daggers combine into one weapon, and the fists do something we haven't seen yet.
That's not to mention the stuff we've only seen in art, like that giant blade in this image:
Which seems to be maybe an 'upgrade path' of the sword that can become the giant hammer?
So no, it's not only 6 melee weapons. Even if it was, which it's not, those six are functionally 12 weapons due to the multiple movesets for transformation.