It would be similar to Explode. With Explode you pay extra mana to get rid of the equipment + get an attack. With the Cursed trait, the player could pay extra mana to get rid of the cursed equipment + get their beneficial equipment. For example, they have a cursed chest piece on you that costs 5. You want to cast your chest piece that costs 6. You pay 11 mana and it is a done deal.
You would then have the question of whether the cursed equipment should go back to the person's spell book or be destroyed. Either way could work, with the spell book option reducing the mana cost necessary to get rid of it. It's just a matter of taste. I would prefer if the Cursed equipment was destroyed.
I still don't like the idea of cursed equipment in general, really. However, if it did make an appearance, that is the best suggestion thus far in my opinion.