The point is they are still an arcane caster, they can't select divine spells because they are divine. The rules very much imply that you can't get spells from another list unless you take the class or you have an ability that says you can. This could be used to negotiate with a DM on maybe Wu Jen or Assassin specific spells, but negotiation only not self-rule and most certainly not divine. My point is that they could make any spell they wish into an arcane spell known.
Right. That's what they can do now. Take a look at the Bard's spells entry: "A bard casts arcane spells,
which are drawn from the bard spell list. "
And the Cleric's Spells entry: "A cleric casts divine spells,
which are drawn from the cleric spell list."
And Druid: "A druid casts divine spells,
which are drawn from the druid spell list."
And the Paladin: "Beginning at 4th level, a paladin gains the ability to cast a small number of divine spells,
which are drawn from the paladin spell list. "
And the Ranger: "Beginning at 4th level, a ranger gains the ability to cast a small number of divine spells,
which are drawn from the ranger spell list."
And the Wizard: "A wizard casts arcane spells
which are drawn from the sorcerer/wizard spell list."
(
emphasis added)
Exact same wording each and every time. With one exception:
The Sorcerer: "sorcerer casts arcane spells
which are drawn primarily from the sorcerer/wizard spell list" (
emphasis and
emphasis added)
Nobody else has that extra word in their Spells entry. Nobody. The Sorcerer entry even has an entire sentence that's not found in anyone else's Spells entry, that strengthens that "primarily": "These new spells can be common spells chosen from the sorcerer/wizard spell list, or they can be unusual spells that the sorcerer has gained some understanding of by study. " -
nobody else has this clause at all.
Unlike essentially everyone else (even in splats - about the only other two exceptions I know of are the Archivist and the Chameleon), the Sorcerer is not limited to their class spell list... although what's required of going out of it isn't defined.