Some clarifications:
Sword of the Arcane Order simply allows a paladin (or ranger) to cast wizard spells using the paladin's spell slots. It does not replace the paladin's actual spell list.
The feat was obviously not written with Prestige Paladin in mind. Then again, a lot of the things in D&D aren't written with other things in mind. The same feat can be used with the Mystic Ranger variant ranger in Dragon 336 to get 5th level wizard spells on top of better ranger casting at the laughably cheap price of a few other class features being granted slower and no animal companion.
Does the feat work in a vacuum with Prestige Paladin? That's very debatable because the feat specifies it uses "paladin spell slots." Even if it is interpreted that all spell slots count, however, this is one of those things you should absolutely ask your DM about beforehand, period. For many DMs the trick will grossly screw with the game since you now have a character who can cast an even bigger array of spells than the DM should normally expect to prepare for with a single character.
As far as other feats go, you might be thinking of
Battle Blessing to cast standard action paladin spells as swift actions. Again, it's something to talk with your DM about because it's really cheesy to combine Battle Blessing with Prestige Paladin much less a Prestige Paladin with SotAO, assuming the ruling is that all standard action spells are effectively quickened because it's a paladin that's casting them.
As far as Battle Blessing goes, the most sane and reasonable ruling for overall game balance and flow is that it only applies to spells that are actually paladin spells. It would not apply to cleric spells for Prestige Paladin nor would it apply to wizard spells through SotAO. If a spell is on the list of both cleric and paladin and/or the list of both paladin and wizard, it must be cast as a paladin with the spell level associated with the paladin list for it to qualify for the feat.
