Concept: reverse Cursed Shield?

One of the characters I'm gonna use, Dynamite Headdy, has his in-game temporary power-ups as his main weapon in my hack. An idea popped in my head: What if I could recreate his "temporary" power-up status for the hack? Then I remembered that the cursed shield, after the number of battles, turns into the Paladin Shield.

My idea was to have the more powerful weapons have a "number of battles" before they turn into his standard weapon. Basically, a reverse Cursed Shield that instead of turning into a good weapon, it turns into a weaker one.

However, I'm not sure if this effect works for shields only, or how can I add them to standard weapons. Quick look into usME gave me no "Curshed Shield flag" so I assume this is all hex editing.

Anyone help?