Is there any way for a anti-paladin to fool a paladin into believing he isn't evil (block detect evil, mask evil powers etc), and if there isn't how hard would building a home brew archetype around that idea be? It's just as is it is very hard for a Anti-Paladin to subtly influence a Paladin towards darkness when the paladin instantly knows the anti-paladin is evil.
Palpatine was more Lawful Evil than Chaotic Evil.
I'm sure you could build a Lawful Evil archetype for the Anti-Paladin, but I think a Hellknight would be an easier way to go about it.
And yes, there are ways of masking your alignment (I think there's a spell even called Mask Alignment).
you probably just need an amulet or ring of constant undetectable alignment, to be honest. the rest is ungodly charisma checks.
Really, really good question, Tameknight. One of the things that fantasy worlds like Pathfinder suffer from, is the fact that morality is so quantifiable.
Undetectable Alignment
http://paizo.com/pathfinderRPG/prd/spells/undetectableAlignment.html
Naturally, an anti-paladin or incredi-evil sorcerer would want this in wearable form, or at least as a potion, which would mean finding a nefarious potion-maker to make you a few dozen, or find an enchanter who has no scruples about concealing evil.
In-fact, it would make sense that the anti-paladin's high-priest would have given such a potent item (only 3000gp I read on some forum)to the unholy warrior as part of a ritual "sanctifying" his status. I'm tempted to make it a rather evil-looking dagger he'd keep on his person at all times, to avoid divining eyes seeing who is whispering dark secrets and sweet dreams into the ears of young paladins.
BUT AGAIN...don't let what is or isn't in the rulebooks get in the way of a great story idea. Who is to say the anti-paladin wasn't darkly blessed with a writhing tattoo of evil down his back, that conceals his alignment and compels him to report back to his overlord once a fortnight? Such things make for great plot-points.
Angelskin