I should stress again that I'm totally in favour of improvisation as a part of learning. But there's no way I'm going to applaud the idea that the bits that you picked up instinctively on talent don't need to be taught, or that they would typically be picked up by experimentation alone.
I think your general point (which you elaborated on in many ways within your post) can be distilled to:
"Students have different abilities and music should empower all of them, not just the few that already have latent aptitude".
... and who could disagree upon that.
I have never been able to draw or paint. I have bought lots of books on the subject and have tried hard and failed. It is an ability I simply do not have. However, when I was a child my parents bought me a "painting by numbers" kit for Christmas one year. I you are not familiar with the concept, a board has a picture painted upon it with many small areas marked out containing a number. Each number matches one of the oil paints. I painted a wonderful picture of two horses in a field that was proudly hung on the wall for many years. But, of course, I still couldn't paint or draw (though I did transfer another artist's creative ability onto canvas).
Would I have been better served with a set of paints, given some elementary instruction upon how to mix and apply them to the canvas, and encouraged to make a mess? Difficult to answer, I really enjoyed painting by numbers and maybe I would have thought myself a failure by making a mess. Or maybe I would have discovered an ability within to express myself via this medium.
When I was a child I was entered into many music festivals by my parents. A set classical piece was played on the piano before three judges. Marks were given for how "well" the piece was played and the winner was the person who had most faithfully transferred the notes written down into piano strokes on the keyboard. I was taught by my music teacher under no circumstances to deviate from the written notation. This would be marked as a "wrong note" and points lost. I suppose you could mark finished "painting by numbers" work in the same way, the winner being the student who had used the indicated color in every case and stayed strictly within the de-lineated patch being painted. And the end result would still be very pleasing on the eye.
I suppose the real debate is whether musical theory is a precursor to musical expression and performance.
We all learn to speak long before we read and write. Speaking requires thought and is always unique. But speaking has its own notation (just like music) which is words on paper. There are people in the world that can speak eloquently but not read and write. Just like writing words, I think music notation is a useful ability, but it does not have to pre-date making music (just like reading words never pre-dates learning to talk). Imagine going to a poetry recital and hearing some great works by Wordsworth and Yeats. And then, afterwards, an amateur recites one of his own, original, poems. Not as good as the great masters of course but still interesting. Which would you most enjoy listening to?
So I still feel it may be worthwhile to experiment with teaching students to play well with a minimal amount of theory and then, if the student so desires, fleshing this out with the ability to sight read and understand some underlying theory later. The input of others (who have had far more experience of teaching piano in the real world than I), would be most welcome (especially from those that have actually attempted such a technique with success or failure).
Topic: Teaching Methodolgies