In the comics, Ra's is the head of a massive worldwide criminal organization seeking to eliminate humanity to restore the world to a perfect ecological/environmental balance. He's also somewhere around 500 years old and he never trained Bruce Wayne. In fact, Batman and Ra's don't meet until years after Batman has been working for a good number of years. In addition, Ra's never posed as 'Henri Ducard'. Ducard is a completely separate character: a brilliant detective working out of Paris who trained the young Bruce Wayne.

The Scarecrow's origin is a bit more complicated than you make it out to be as DC keeps on revamping and reworking the character, even turning him into a mutated monster for a time.

And I've already pointed out in my review why I consider THE DARK KNIGHT's Joker to be 'a' Joker but not 'The' Joker so I'm not going to beat a dead horse by going into it again here.

The point is that the Nolan version of Batman isn't following DC continuity to the letter so why not introduce Barbara Gordon as Oracle? She doesn't have to be Gordon's daughter. She could be his niece Barbara (and don't give me that look...I'm sure you've got family members who share the same name) come to stay with him in Gotham due to her parents passing away in a car accident that leaves her paralyzed. While coming to grips with her disability she finds new purpose in her life by becoming Oracle.

In the movie, Ra's is the head of a criminal organization of unknown size, seeking to eliminate humanity to restore a perfect ecological/environmental balance.

Ra's may be 500 years old, the movie doesn't say. Although some guess that he's not, since it's supposed to be 'more realistic'.

Even if Batman never did fight Ra's until later, their meeting had little effect on other events. Whereas with Oracle, that's very specifically after Robin, Bat Girl, etc.

Also, Henri Ducard is a fairly minor character in the Batman continuity. Oracle, on the other hand, is important.

There's a difference between tweaking the continuity, and smashing it with a sledgehammer.

In the movie, Ra's organization is most certainly not a criminal one. In fact, the whole thing is that they're out to destroy criminals. That's why Ra's wants to destroy Gotham, because it's become so criminally corrupt. In the comics he's an eco-terrorist more than anything else who is using his criminal organization to achieve other goals.

And I don't see how Henri Ducard, the man who taught Bruce Wayne how to be a detective can be dismissed so casually as a "minor character". The extreme changes in both Ra's Al Ghul and Henri Ducard from their comic book incarnations to the movie versions don't qualify as major continuity changes but introducing Oracle before Robin does?

I'm pretty sure mass murder on that scale counts as criminal.

Also, in the comics, Ra's often cites mankind's corruption as reason for killing them.

As for Ducard, maybe it's only my point of view, but I'd barely heard of him, and many other Batman fans probably haven't heard of him. Everyone who follows Batman knows about Oracle. And Ra's often impersonates people (although I admit, that's a bit of a stretch).

Her coming before or after Robin may not be that big of a deal, but her being Gordon's daughter, being the former Bat-girl, and being shot by the Joker, are all integral parts of her character.

But the Ra's Al Ghul of "Batman Begins" certainly didn't see himself as being criminal and indeed had extensive and lengthy dialogs with Bruce about the nature of criminality and why he hated criminals himself. It was a hatred he and Bruce shared but Bruce refused to kill criminals and Ra's did. Like 90% of fiction's best bad guys, Ra's didn't see himself as being the bad guy. As far as he's concerned, he's the good guy.

Let me see if I've got this right: because, as you say most Batman fans haven't heard of Henri Ducard (and most of the Batman fans I know have heard of Ducard as he's not as obscure as you'd like him to be) it's okay to change him to suit the needs of the script and story but it's not okay to change Oracle because you claim she's more well know.

I could be wrong here but I'm getting a distinct vibe that your argument is mostly based on you liking Barbara Gordon/Oracle and not wanting to see her character changed for the movies. And there's nothing wrong with that. My argument is simply that a Barbara Gordon/Oracle in Nolan's version makes more sense and is more consistent with the tone of the two films and would be more of a fit than a Barbara Gordon/Batgirl

I'm pretty sure the Ra's of the comics feels the same way.

Before Batman Begins, I'd only heard of Ducard once or twice, and while the name sounded familiar in the movie, I wasn't sure why. I'll admit, I'm know a fair amount about Batman, but am not an expert by any means.

Yes, I do like Oracle. Just like I like most of the characters in Batman's world. I'm against any major changes to the storyline. And Batgirl/Oracle is a MUCH bigger character than Ducard.

That said, while it would be a huge change to the continuity, and I am against it, it wouldn't be the end of the world. It would definitely be disappointing, but I'd deal with it.