Great ideas. I especially like the seasonal changes.
I'd like to see every mob in the game, from a marmot to an Ogre, be a potential place-holder for one (or a few) of the biggest, baddest HNMs in the game. Not only would we avoid the tedious camping but how great would it be for Tiamat to pop right outside of Ul'dah because her window was up and some level 3 killed a beetle?