Regarding your first point. Do you think the developers expected competitive battling or did it come naturally from those who created it?
Nuzlocking is a self restriction we set on ourselves to make the game more interesting. I am speaking of a development standpoint.
There's a lot here, sorry for the rambling.
Tournaments with prizes had to be in the minds of a battle-focused game from the start, to make it a worldwide phenom. A point to this focus on competitiveness is that they've introduced typing accordingly. Psychic-types lay waste to everything in Gen I? Hello, steel and dark. The dragons are over-powered? Fairy typing arrives.
Children can go on their merry way, but then they can they discover the hidden side (though you can never really go back).
About Nuzlocke, hence why I said "self-imposed." I think it speaks to the fact that we don't
have to rely on the game out of the box. Regardless of how pokemon expands, experienced players will always find a way to make things interesting, as it's a two-way flow of innovation. One has to wonder how GameFreak factors this player creativity into their changes and progress.
But back to your point, I think how the AI improves makes a major difference. Were the AI to start switching more aggressively, we'd have a far more difficult experience (Battle facility strategies, for once, would have to change dramatically).
I also wonder why they had a challenge mode in B2/W2, but it was nowhere to be found in X/Y. Hopefully not a one-game wonder, or starting a trend toward the easier experience.
What do you think about where they are headed?