Awesome that you wanna add this function, thank you!
I took a look at the <Forbidden Wtypes: x y z> function and it turns out when you have a claw in you your offhand equipped, you can only select claws for the mainhand. This works fine as the description of the function says, but wouldn´t it be nicer if you could select also all the other weapons the character could equip?
Lets say you have a claw in your offhand, it still let´s you equip all the other possoble weapons in the mainhand, but if it´s not a claw ether, it should clear out the offhand. With this version the player could always see all the weapons he can use on the character.
Maybe this is an interesting mechanic you wanna add? But it is not really an important one xD