Could the Incantifier Prestige Class be improved?

The Incantifier is a 5-level long prestige class originating in Dragon #339, which was created to allow for PCs or NPCs who belonged to the Incanterium - a historical Planescape faction that believed arcane magic was the ultimate source of power and which devoted itself to magic's mastery, until some unknown catastrophe warped them into strange, quasi-immortal magic-eaters. It grants characters the following traits:
* 2 free metamagic feats (2nd and 4th levels).
* Spell Resistance (20 + Incantifier level) and the ability to use either Spell Eater or Spell Leech if the SR check is successful.
* Spellcasting: +1 level of existing arcane class (1st, 3rd, and 5th level).
* "Arcane Body" at 1st level (immune to aging/no natural lifespan limit, immune to hunger, thirst & fatigue, but cannot heal except by using Spell Eater).
* "Spell Eater" at 1st level (heal 1d4 hit points per resisted spell's level) and "Spell Eater II" (consume single-use magic items and magic item charges to heal as per Spell Eater) at 3rd level.
* "Spell Leech" at 1st level (recover 1 expended spell of equal or lower spell level to resisted spell) and "Spell Leech II" (drain charges from staves and wands to replenish expended spells) at 5th level.

All in all, this isn't a bad PrC and it does pay considerable homage to the original Incantifer monster. I'm just wondering if maybe there's an area or two that could stand to be strengthened? Primarily, I'm wondering if only +3 spellcasting levels and 2 metamagic feats makes sense, and if maybe the Spell Resistance trait shouldn't be stronger - in 2nd edition, Incantifers had a base magic resistance of 20% starting at 9th level (the lowest you could be transformed), which improved by +5% per level over 9th, so a 20th level Incantifer would have a 75% Magic Resistance plus the spellcasting abilities of a 20th level Mage or Specialist Wizard, whilst a Wizard 15/Incantifier 5 would only have 25% Spell Resistance and the spellcasting abilities of an 18th level Wizard. I don't know, maybe I"m just thinking about this in the wrong way?