you can destroy the parts and create a complete weapon when the weapon is made. one single object for the whole weapon. if you break a weapon in the anvil, it destroy the weapon and creates the itens again. if you don't atach the pieces, but destroy the parts and creates a whole object as the weapon it may work better.
Like, if I atach a guard to a grip, it destroy both itens and creates a new piece. You would have to create every combination, one hand guard and fancy grip, one hand guard and normal grip...