Hot Take: DAK is the least hottest park at WDW. Yes it's mostly outdoor, but the trees offer a great amount of shade unlike the concrete expanses of MK or Epcot.
To me, DAK feels like the hottest because the air is always very still. The vegetation keeps the humidity up and prevents any breeze from making it down to ground level. But you may be right, the outdoor portions of DAK are better shaded than any other Disney park, and that probably does actually translate to the lowest temperature. (If you were to average the temperature experienced across the day, though, Epcot would probably fare the best, since every attraction is indoors and has significant indoor queues.)
For many years, I wanted Disney to make a 5th gate; a coaster park; all coasters; and make it a villains park.
Take off the shelf coasters and Disney does what it does best and theme the heck out of them, adding high quality theming to them and adding dark ride elements to them.
This would be great for the older kids and young adults in the family.
I also know it will never happen,
Wouldn't it be better for those 15-or-so attractions to be spread among DHS and MK instead?
I also think even though I personally really want it at Magic Kingdom, the fact that it is being considered for Hollywood Studios is a good sign they are keeping options open and are continuing to develop it.
I just hope the program of such a land has a variety of attractions and thrill levels.
MK has a small enough roster of thrill rides that a hand full of rides appealing to that group that it could be easily added to the lineup in a constructive way.
DHS needs to build out it's child and general audience ride lineup before they should seriously consider adding more thrill rides. I was a ride operator at DHS for a few years before the big transformation, and while at greeter, I would get asked almost daily to make recommendations for rides that family with a smaller kid or grandma could ride. You could see the disappointment when you tell them that basically all there is to do is Midway Mania, Backlot Tour (it closes at 5 and has an explosion and earthquake) and Great Movie Ride (depending on how scared they are of Alien, gangsters with loud guns, snakes, and skeletons).
Disney theme parks are at their best when they are thought of as having to cater to a general audience. You can have particular attractions that appeal to thrill lovers, small children, nostalgic grandparents, and combinations thereof. But each of those groups should have a whole day's worth of stuff for each group, otherwise the park will feel incomplete.
MK and Epcot are a bit lacking on thrill rides, DHS is lacking in family rides, and DAK could use two or three more things for every group.
Each park should have a distinct theme, yes. But each park should cater to the same broad audience. After all, Disney's core clientele is spending all week at the resort. Every day should be full of great stuff to do for each group, instead of each day catering to one group above all others.