First of all in that mmorpg players do not look for their objects depending on the statssThe second thing about this is that it is not something that of a buff or nothing, it is only DECORATIVE and I emphasize again DECORATIVE, it serves to identify the class with which a player plays
So instead of creating very complex new weapons, the only thing they have to do is a minimal decoration that accompanies this magic mesh.
Apart from all this I do not understand why you are talking about the stats , if this is due to transmog, there is no problem because you can literally change everything in transmog zone.
What I mean, while talking about the stats, is that reducing the amount of type of weapons will reduce weapon type limitation per class while looting, so at raids every peace of loot will be usable for more classes or people. So if there are less types of weapon classes will have to search weapons by stats instead of by type.
You said that bard instead of having his own type of weapon (instrument) will use a bow with a esthetical change, so bard will have to loot bows instead of instrument. If you plan to do this with a lot of type of weapons that means, for example, there will not be dagger in the game because classes with dagger will loot swords with an esthetical change to dagger. Other example is that voodoo dolls for witch will not exist in the game and instead will have to loot a rune that esthetically will change into a voodoo doll, and that rune will be looted by every caster that will transform that rune esthetically into an exclusive class item. If you do this every melee class will loot only swords, caster will loot only runes and rangers will loot only bows, because instead of having their own type of weapon they will share types of weapons but with an esthetical class exclusive change.