Here is another poll, this one on BR paladins. When it says per the PHB that means all paladins are the same, but they still have to gain their abilities from one of the deities - i.e., BR paladins can't serve just a cause. This is to keep the flavor of the original setting intact.

I didn't add the choice of using prestige classes, since using them is something that people tend to do instead of using the standard paladins from the PHB, basically an overall house-rules thing. It also requires at least a 5th level character to qualify for a prestige class (per the 3.5 DMG, pg 197).

Complete Warrior gave an example of an alternate paladin that can be used for rewriting the classes. Rewriting as a new class entails any aspect of the class, hit dice, BAB, saving throws, class abilities, spell lists, etc. - so if you are considering this option keep in mind that nothing about the paladin class in the PHB can't be changed.

Forgotten Realms Campaign Setting gave examples of paladins that can freely multiclass with another class.

Again we need to keep the required books to use only the core 3 (or SRD).