Interesting concepts.
I came at this article wondering if it would be similar to several arguments I've heard regarding the purpose of the "Easy" difficulty setting. Some want a cakewalk, some want a respectable challenge that's a tuned down "Normal". Personally, I'd say the Bioshock Vita Chambers represent what I'd call an "Easy difficulty caveat". Playing the game on Medium with and without the Vita Chambers creates such a large difference in play style. Originally I'd considered concepts like that should be adopted as a means of broadening the appeal of a game to a wider audience. "Casual" gamers aren't necessarily people who don't want a challenge; they may simply not want the repetition of reloading a save or replaying a checkpoint.

I'm very interested in Tomb Raider's difficulty adjustment, however, because it catapults difficulty beyond pigeonholes of Easy, Medium, Hard etc.

Presumably, one could adjust the game to their preferred playstyle. I often find it frustrating that harder difficulties merely increase opponent health and decrease player health. I don't mind the latter so much, but the former feels cheap, particularly when it pushes the player into repetitive, frugal tactics. Giving power to the player in this sense, could breathe a lot of life into games that would otherwise stagnate over time.