We all know that DH is an unholy mess of stuff being dropped on the readers' heads that were neither mentioned nor hinted at anywhere in previous books. But there's one subplot I wish had been introduced earlier, because it carries a lot of potential for conflict, and with conflict comes plot and character development and all that. I am referring, of course, to Dumbledore's backstory.
What if Harry had found out about Ariana and Gellert and the rest while Albus was still alive? Would he be able to look his Headmaster in the eye, knowing young Albus had once plotted world domination with the future Dark Lord Grindelwald? Would he realize how narrowly he'd escaped going mad, like Ariana, after living with magic-hating Muggles for ten years--Muggles that Albus
placed him with, no less? (Seriously, why did no one catch that plot hole? Even I didn't see it until guardians_song
pointed it out.) How would this change things?
But we can't have any of the above, since the plot of DH depends on Harry obeying Dumbledore absolutely. (I've been meaning to write something about how post-GOF Harry fails at the Hero's Journey. Remind me, will you?)
There's also so much potential for fanfic, and I don't mean just the Grindledore variety (though one can never have too much of that! *Grindledore shipper*). We've all seen those dreadful fics tagged "Powerful!Harry", "Independent!Harry", "Super!Harry", "Dark!Harry" or whatever, in which Harry becomes a Gary Stu of the highest order, usually with super-powerful wandless magic. Well, guess what? Thanks to Ariana, you can still have a Harry with super-powerful wandless magic, he'll just be mad. And I don't know about you, but I'd LIKE to read about mentally-ill!Harry.
So what do you think? The possibilities are endless!