I have similar experiences. Having trained primarily ITF TKD, I can either be a poor kickboxer or a mediocre TKD practicioner. The latter is usually more effective when sparring.
I'm somewhere in the middle. A lot of people are saying that Machida is a unique athlete, like Anderson Silva and GSP, and would probably be a world class fighter no matter what his discipline would be. It's the Bruce Lee-esque idea that the style doesn't really matter, I suppose. He primarily uses elements from karate, but I'm quite sure he would be pretty bad-ass if his father was a Wushu sifu (or whatever the term is).
I kind of agree with that. I disagree that it's a waste, because not all martial artists are focussed on full contact fighting. Furthermore, there are some TMA schools that have basically become kickboxing-TMA hybrids in order to be more effective in TMA sparring competitions. But I do agree that there is a lack of recognised TMA schools (and organisations) focussing on TMA-style sparring for the purposes of full contact fighting.
There are some karate styles, I forget their name, which do not teach any blocks at all. Only movement, attack and counterattack. I wouldn't it put it past Machida's father to steal elements from other styles of karate, nor would I simply assume that all the non-shotokan techniques Machida uses are from muay thai. Elbow strikes were not invented in Thailand.
As you say, it is doubtful that Machida will change karate schools in the near future and I don't think any MMA practicioners will begin training karate because of Machida either. Work more on sweeps and trips, probably. But not step into a dojo as a white belt karateka.
Ditto. I hope that, in the future, there will be many different styles of "kickboxing" schools. Right now, you have the traditional kickboxing organisations and the muay thai, both of which are almost completely focussed on sparring. (Some kickboxers do the musical forms and whatever) Maybe in ten years, you will see shotokan-based kickboxing schools, TKD-based kickboxing schools, and if Cung Le doesn't retire to become a movie star, more Wushu schools.
The major TMA organisations won't change though. Not in a million years. Too many masters who are fond of katas.