I'd like to start by saying this is my first post. I've been playing 3.0 and 3.5 for only a few years, so I am not new to the game, but no professional, either. I haven't involved myself in the internet community surrounding the game very much, but it looks like fun!
The challenge of defining the Paladin class comes from the fact that there are class (or class combinations) that evoke the Paladin theme more powerfully than the class itself. It is an interesting exercise to create a Lawful Good Cleric that can outshine a Paladin in frontline combat as well as supporting roles yet hold the exact same ideals (and thus, roleplaying challenges) as the Paladin. The only tradeoffs are the rounds the cleric spends enhancing him or herself (or others) to achieve those results (and, if on a mount, then it is an easier target than the Paladin's). More interesting still are the fighter/cleric combinations to further improve frontline combat effectiveness. Still, if we as a community really believe a Paladin to be distinguished and canonical enough to be a class apart from the Cleric, then the following shall indicate my preference on the debate over alignment.
A dictionay definition of Paladin:
American Heritage Dictionary via dictionary.com wrote:
1. A paragon of chivalry; a heroic champion.
To define chivalry:
Dictionary.com Unabridged v1.1 wrote:
1. the sum of the ideal qualifications of a knight, including courtesy, generosity, valor, and dexterity in arms. 2. the rules and customs of medieval knighthood.
Regarding Paladins and the alignment restriction:
d20 SRD via d20srd.org wrote:
Lawful Good, "Crusader"
A lawful good character acts as a good person is expected or required to act. She combines a commitment to oppose evil with the discipline to fight relentlessly. She tells the truth, keeps her word, helps those in need, and speaks out against injustice. A lawful good character hates to see the guilty go unpunished.
It's based on this that I cannot dare to see anything that isn't lawful good as a Paladin. The fact that chivalry is defined by rules and customs as well as a set of positive ideals represents lawful and good, respectively.
I agree with the debate that to be restricted so should allow for a class with superior options. I will reserve my vision of the Paladin class, one that hopefully preserves backwards compatibility, for another post.
P.S. A class with a real alignment problem would be the Rogue. The class allows Alignment: Any, yet the dictionary defines a Rogue to be a "dishonest, knavish person" and this definition is reflected in the Rogue's class skills! (i.e. Bluff, Forgery) That rules out lawful immediately!