Could you add an event (like the frost/pumpkin moon) that's post skeletron, and meant to provide you with weapons/armor capable of killing the WoF? (I was figuring the event would be demon/fire/hell themed, and could only be fought/summoned in hell.) For example, it could add an item that can turn molten armor into a new armor that buffs all weapons instead of just melee, and has an extra three or so defense. And it could add upgraded forms of weapons found in shadow chests, like a sunfury that has a ring of spinning sparks around it, and a dark lance that causes a wall of shadow-tridents to move across the screen in the direction you stabbed in, or a hellwing bow that fires arrows in sets of three, like a lesser tsunami. Or maybe they could just be the same weapons but with more damage/speed.
More good weapons from the pirates and frost legion would be good too, and less hard to make.
Also a post-golem ore that can be crafted into a general armor set and various weapons would be nice.
Not that I'm expecting you to do all these things. A couple would be cool though.