I think they should have used the Suicune approach for the trio in B2W2. Rather than have them just standing there out in the open waiting for you, they'd first play a game of run and chase instead before you finally get to battle / catch them. At least that would have made it a little bit more interesting.Playing B2W2, I liked that concept that they were looking for you, but gameplay wise, it made it boring. So while it has a good reason, it's still something I wouldn't want to see in XY or subsequent games for that matter. The saving grace for legendaries in B2W2 is that there are a few you have to actively seek yourself, so just those three being out like "hey here I am" is overridden by many others that need more effort.
On the contrary, I would love to see more puzzles involved. Those were a ton of fun in my opinion. It doesn't have to include Braille like in RSE, but something similar would be nice. Anything to add some challenge to the hunt for the new legendaries.well not something as hard like the regis in RSE but with a bit of challenge