Re: Why did the League of Shadows want to destroy a peaceful city?
If I can be a conspiracy theorist for a moment, I always thought it was kind of interesting that they list Talia as Ra's daughter in his bio on the BB special features. The bios were meant to be for the in-movie characters, not just random trivia about their comic book roots. Nolan is known to be pretty involved with what goes on his DVDs.
I also thought the rumors of Nolan being upset about the Justice League: Mortal film because it featured Talia trying to avenge her father's death interesting as well.
Not saying they had it planned all along, but it could have been something they were toying with in the back of their minds, or something they wanted to have the option to do if they saw fit.