Saving Throw bonus from Armor enchantment

[WizWom]

In PnP, Magic Armor give s a saving throw bonus to attacks one can reasonably dodge; such as, for instance, a fireball or Lightning bolt.

 

The problem, of course, is that there is no in-game way to give a bonus to saving throws only verses certain attacks, right? Is there any way to give a saving throw bonus against directed spells, but not area effect spells - yuck, even THAT wouldn't do it right. Gah. Would we have to make saving throw bonuses against every possible effect which armor should help with?