I do think that the Magic Kingdom could use another thrill ride, but I agree - it's not the park to put in an ultra intense attraction. You mentioned capacity, and a new thrill ride would help that because it is actually an issue that needs to be addressed. However your point is well taken. A thrill ride of the scope of Everest would not have the same effect on the Magic Kingdom as it did to the Animal Kingdom.
I also agree that the MK is the park of least need right now, but it is the park that is currently getting additions. I do like the scaled back look of DL's PH, but I just don't see the need to have as massive a section as it appears to be for WDW's version. I just think the discussions gotten away from land use and into what each park needs. I think if they do PH, they have to some kind of attraction to go along with it. My wish is that they would make a dark ride coaster, much like Universal's The Mummy, but whatever direction they go, I just think one additional attraction should be added.