1) I think it should be disallowed if it fails to make sense. Not all things are valid possibilities, simply because they can be imagined. If, for instance, iron interfers with magic, "I want to play a mage that wears full plate!" is probably not a reasonable idea.
If it doesn't make sense
to you you mean. You want to be the judge of what character concepts are reasonable and what aren't without even looking at the concepts. Iron, by the way, doesn't interfere with magic in D&D, unless that's your personal house rule. Cold Iron does, a little, but it's just that it's hard for mages to cast without full mobility. However, with training they can do it just fine (see Duskblades).
2) Because seriously, someone being a Paladin is a path that would demand a great deal of focus and concentration on that path (though not necessarily the class by that name).
Why? That's not what historical paladins were. They were just loyal warrior servants of someone (originally, the king of france). That's it. Just warrior servants. Now, you who think you are judge of all character concepts may say "I think paladins require great focus and concentration" but that's how you should play your paladins, not how everyone else should play theirs.
3) No, the very idea comes from the theory (unfounded, perhaps) that Charlemagne's "paladins" were upholding Go(o)d and King.
Yeah, that's exactly what I said. Here, I'll quote myself: "a "Paladin" was just an elite guard dedicated to a lord (specifically, in France, a long time ago). The very idea of a Paladin as servant to a great god comes only from the divinity of kings and the idea that whatever the king said was good." Charlemagne's paladins were guards who followed his orders loyally, and thus were serving God due to the divine right of kings.
The peers were supposed to be heroic, not merely warrior vassals. In fantasy, the term has been used to mean specifically the Lawful Good by-whatever-name chivalric and pious ideal, as a general rule. A person dedicated to selflessly serving a God bent on destroying all life is not closely enough related to this kind of champion to merit the same class being used.
No, historically in D&D and a few other offshoots Paladins were lawful good. However, that hasn't been true since Unearthed Arcana, which already introduced other sorts of paladins. And again, that's your opinion that paladins can't be evil. So, you shouldn't play evil paladins. But if others are having fun with evil ones, they should be allowed. After all, the point is to have fun. I have one in my party, actually... a Paladin of Tyranny/Hexblade/Ur Priest/Bone Knight who is a loyal guard of my Necromancer.
4) I have nothing against having a "Circle Mage" prestige class (or even variant/option/feat for a regualr wizard). But if you want to be a "Red Wizard", you have to take the rest of the package.
This is exactly why having too much fluff ruins classes. The "Red Wizard" could easily be renamed "Circle Mage" and lose a few alignment requirements and suddenly it would be a better class, because it could still be used to create a Red Wizard concept, but it could also be used to create other concepts (namely, good ones). That's exactly the point. A class that has a bunch of extra fluff thrown in that forces you to do something if you take the class that, fluff wise, you don't want is a problem. This is the same issue with paladins... just change it from "they have to be lawful good servants of god" to "they have to be servants of something" and now it can do all the same character concepts as before, plus a bunch more. You oppose this because you're used to the problematic class.
Giving players the option to do anything, no matter how absurd, because "they'd have fun with it" is not a good idea.
Yeah, how dare players have fun. And remember, it's the DM's call whether something is absurd. You're trying to judge absurdity without even hearing the character concepts. You just think a Monk/Barbarian must be absurd, despite the fact that you hadn't even heard character concepts that fit it. Better to let the DM decide if a character doesn't work after hearing it than for you to decide when you are acting, once again, from ignorance.
It would be ludicrious to ask to play a paladin (the standard, LG, etc. kind) in Middle-Earth or Conan's world, or settings inspired by one of those.
Why? I want to be a Rider of Rohan who's dedicated to serving his lord, and through his faith finds power. Maybe take the spell-less varient to match the magic light setting. Is that ludicrous? It seems to me you just once again banned a large number of character concepts because you didn't think about them.
It would not be a good idea to allow wuxia-style monks in a game telling adventure/horror in something equivalant to Dark Ages Scandinava.
I want to play a savage warrior who can take on fully armoured knights with his bare hands. Bad idea? Why? I wasn't aware that, stripped of weapons, Beowulf was a pansy.
As noted elsewhere, as well: What's the role of a class if a class-based system is designed to be able to potentially do any kind of character imaginable?
I answered that last post: "Isn't the point that the mechanics allow people to, in a a balanced and easily representable manner, play whatever sort of character they want to play?" You want to play a thief character who's strong with a rapier. Your buddy wants to play a shapeshifting nature character. Now, how do you do that in a way that's balanced? If the classes are balanced, you be a Rogue 12/Swashbuckler 8 and your buddy plays a Wild Shape Varient Ranger 10/Master of Many Forms 10 and now you have mechanical representations and rules for what you wanted to play that balance out. That's the point.
I don't think "I don't like this, therefore it should not exist", I simply don't believe that players should be allowed to choose anything they want, no matter what it is.
That's a contradiction. You just stated a bunch of things you didn't like (various paladin types, for example) and said they shouldn't exist. What you believe is that you're the judge of what character concepts are reasonable, not the DM who actually hears the concepts. You think it's the job of mechanics to constrain fluff to within the perameters that you think are proper.
JaronK