Doctor Shaft said:
It sounds like a cool idea, although if I were DM I'd immediately discount the succubus' powers. No more summoning demons, even in distress. I'd let the succubus keep the energy drain ability... but would completely forbid its use, lest the paladin wish to kiss her status good-bye. I'd leave the energy drain ability merely as the temptation

. Kind of just look at the player and say "Yeah, you can use energy drain... but the consequences are grave." And then leave it at that.
I wouldn't do this. I'd just say to the player, "Use any powers in a way that isn't Lawful and Good, and you're not a Paladin." Simply becoming a different alignment isn't enough for a demon to lose her powers. The only place I'm aware that we see rules for such things is in Divine classes, and a succubus' powers are innate, not given by a Power.
I see no reason for her not to be using Greater Teleport, or Etherialness, Polymorph, or even Charm Monster. Suggestion gets a bit iffy, but I suppose it could be used safely, with great care. Detect Good is fine and dandy. Energy Drain... That one's up for grabs, cuz I don't know how it's described in the book and IDHMBIFOM.
That said, without a helm of opposite alignment, it's a stretch to see a Succubus even getting to Chaotic Neutral. I'm playing a Half-Demon who's CN, which is often difficult for her. CG is very, very far away, and LG is "Never Gonna Happen." As cool as a Succubus Paladin is, and it
is cool, this character will have to be just about THE most messed up Demon in the history of Ever. Self esteem issues, guilt; she's not going to be a happy person most of the time. She's from the Abyss, she knows how bad bad can get. she knows she can never defeat the lower planes. She knows better than any mortal does... And she's a traitor. Top priority for slaughter. Both Hell and the Abyss would have her on their extinction list. Hope she has some powerful friends. VERY cool concept.
- Kemrain the Chaotic Neutral [Evil].