Good idea, but the problem here is you're adding an extra step to combat - which can already be cumbersome. By giving each set of phantom armor a set of its own hit points to track, which the illusionist and the GM then have to remember and then determine if an attack missed but still wold have hit the phantom armor but not the illusionist, I'd keep the AC of the various phantom armors and just say "Leather Phantom Armor: AC 8, absorbs one successful melee or ranged attack's damage then vanishes, lasts 1 rd per level" Keeps it simple with the same effect. Do the same with Phantom Chain: AC 5, absorbs 2 successful attacks, then vanishes, 1 rd per level duration." Phantom Plate - AC 3, absorbs 3 successful attacks, then vanishes, 1 rd per level duration."
Good idea, but the problem here is you're adding an extra step to combat - which can already be cumbersome. By giving each set of phantom armor a set of its own hit points to track, which the illusionist and the GM then have to remember and then determine if an attack missed but still wold have hit the phantom armor but not the illusionist, I'd keep the AC of the various phantom armors and just say "Leather Phantom Armor: AC 8, absorbs one successful melee or ranged attack's damage then vanishes, lasts 1 rd per level" Keeps it simple with the same effect. Do the same with Phantom Chain: AC 5, absorbs 2 successful attacks, then vanishes, 1 rd per level duration." Phantom Plate - AC 3, absorbs 3 successful attacks, then vanishes, 1 rd per level duration."