Occult Priest and PrC interraction questions

[Xuldarinar]

Occult Priest (Secrets of Pact Magic) is a class wrapped around binding and casting domain spells. Their spellcasting functions as follows: they gain the knowledge domain at 1st level, and learn an additional domain at 3rd, 7th, 11th, and 19th. They gain each spell usable 1/day, as divine spells, and gains the domain's ability. If they select a domain a second time, they gain an additional use of each spell, and gain bonus spell uses based on wisdom. Their caster level, and highest level spell they can cast, is based on their binder level. Spell DCs are based on Charisma. Granted abilities from binding are Constitution based.

1: Would you permit this class to qualify for binding PrCs from ToM? (Secrets of Pact magic classes bind spirits, ToM binders bind vestiges. Practically identical, just different label.)

2: Would "Soul binding +x" advance this class? (SoPM uses "+1 binder level" )

3: Would you permit this class to qualify for divine spellcasting PrCs? (it technically does cast divine spells)

4: Would "+1 level of existing divine spellcasting class" advance this class's spellcasting? If so, would it advance binding as well or would that be kept separate? Would this option also increase the highest level spell an occult priest could cast?

[Psyren]

Keep in mind I've only read the Pathfinder version ("Pact Magic Unbound") and the Occult Priest is a cleric archetype there rather than a different class, so the exact wordings may be different. Having said that:

1) For obvious reasons they had to be circumspect with the pact magic terminology and not make it too close to WotC's version since ToM isn't OGL. But it's pretty clear that the Occultist's Spirits and the Binder's vestiges are meant to be one and the same.

2) Yes but there is a key difference between Occultist pacting and Binder pacting - namely, the ability to bind more than one spirit/vestige is a separate ability that only pure Occultists get. So even if you equate the two and allow, say, an Occultist or Occult Priest to enter Anima Mage, if either of them did so they would never gain the ability to bind more than one spirit at a time.

3) Certainly but only two classes in 3.5 (Anima Mage and Tenebrous Apostate) advance both divine casting and pact magic, so any other choice of PrC would only advance one or the other.

4) By RAW it would not, because most of those classes specifically do not advance any other class features you may possess. Some advance turning and casting, but pacting is not turning. Only a class like Legacy Champion (that specifically advances everything) or a class like Anima Mage (that specifically advances both), would advance casting and pacting simultaneously.

But there's no need to PrC at all if you use the Occult Priest archetype, which advances your binding and casting anyway.