Can of worms Jimmy..
Ah Moley - even a humble worm needs someone to rip off the lid to let them see the light of day every now and again

My personal belief is that if you look at the kata as a whole from the perspective of Bunkai then the effective Bunkai becomes meaningless.
I tend to agree that it's "more likely2 that the original intent of each Kata was NOT one long combat sequence against a preset group of opponents that you would work through in order - after all they wouldn't wait in line now would they ? (Unless in a McDojo perhaps.....)
It's much more likely IMO that each Kata is built up from/built around imparting sequneces of techniques/appropriate responses to a "set" of defined "Defense Situations" (if you get my meaning...)
I believe that a sequence from a kata ( to be effective Bunkai) is
a) Slightly different to the actual move/moves in the kata in terms of direction, target and follow up moves.
and b) Totally different and separate from the preceeding and following moves in the kata.
a) I agree entirely that the Karateka is/should be allowed a "certain leeway" in their interpretation on the most appropriate Bunkai response to the Defence Situation
b) I think this follows on ( I basically agree) from the concept of Kata being comprised of sets of defence drills - as opposed to a single attack scenario with multiple opponents etc....
I also believe that most of the other moves are just surplus packing to "fill out the kata"
Well Now..... I'm not so sure about this one...... My "doubts" (around your Sanity Moley - LOL) probably depend on YOUR definition of "the other moves".......
What I mean by this is that I certainly think that sometimes Kata contain "repeats" of a Defence Combo on/in other directions (left right - back forward angles etc.) to either balance the look of the Kta Embusen and also to perhaps train both sides of the body.....
I don't necessarily agree that things like Yoi and Yame Opening/Closing movements are "filler".....
So to me it's a way of learning a specific technique or Bunkai against ONE attacker and not a sort of mass brawl. Of course there may be several of these ONE attackers in a kata
Absolutley !
However... as a whole... to me a Kata is a Kata... and a very useful thing it is too.
Anyone for "Spirit of Karate" here ? LOL - Definitely Agree - I'f I absolutely HAD to choose one of the three K's it would have to be Kata