[Snake]

Rather than going backwards, I think it'd be more interesting to push this armor forward. Make it grant an unique Self-Destruct skill as a bonus effect of the armor.

Reactive Self-Destruct

6M

With some inspiration from a certain monster, you've learned to make the craziest use of this torso. Upon use, you'll overload and make your armor explode violently, nullifying any absorption or immunity and setting your own Fire Resistance to 0% (if it is higher than 1), and dealing (300% Fire ATK + 40% Max. HP) as protection and evade-ignoring damage to yourself and all enemies within 4 range, leaving Cinders equal to half of the damage.

Afterwards (if you survive...), you will gain Fiery Armor and Burn LV50 for 5 rounds, but your armor will be unequipped until the end of the fight.

Ta-da.

Though one thing I agree with is Fiery Armor behaving like Armor of Nails at the very -least-.