Bernhard, I truly did find your thoughts very interesting (in fact I copied your post into my Word files of piano teaching tips).
Thank you, I am happy you enjoy them.
But you seem to be over-stating your point a bit.
My sole purpose is to make what I am saying as clear as possible. I find very difficult to express some of these ideas in writing and very easy for the person reading it to get the wrong idea.
In no way do I propose that these ideas are the ultimate truth. Quite the opposite, I myself frequently change my ideas (I will let you know next time

)
I have never, until reading your post, even thought of or heard of teaching both clefs together. I have taught clefs separately for years, and did not "live to regret it."
No problem. Mankind lived for 2 million years thinking the earth was flat and they actually did fine. The question is: Now that this possibility has been raised what are you going to do with it?
I suggest that a most profitable approach is to suspend judgement and discussion for a while and try it out. Maybe it will work. Maybe it won't. Maybe it is not working because you have not understood the idea properly or because the idea was badly written. Maybe it will not work because it is a terrible idea.
I firmly believe in the scientific method: faced with a new idea I take two students. I apply the new idea in one of them, and the other I keep teaching the way I always did. Then I check the results. whatever ideas I suggest in this forum have been through this procedure.
It is only after one has tried out an idea that discussion that is truly useful can be undertaken.
I do plan to use some of your ideas, in showing how the 2 clefs relate to each other (I already do try to show this, but not in the ways you mentioned). But it seems that many young students would do better with small bits of information at a time, rather than the whole big picture. Apparently many experts in piano pedagogy agree with that.
Of course, one should proceed in small bits. That is why, for instance I spend a long time on the staff and only add ledger lines later, much later. It is also why I first teach the score without the piano and only later I will introduce the keys that relate to the notes on the score. At this initial stage is no big deal to introduce both staffs simultaneously: it is still a small and manageable bit. Teaching the grand staff is far, very very far from being the big picture.
However, if one follows certain methods - and I am not saying you do, I am just pointing out that they exist - that start by having only the G clef on both hands and proceed for several months wiht only the G-clef, that is, teaching everything with only the G clef, this will cause a mental block. There is no discussion here, just facts. Try it with two pupils and compare the results.
As for pedagogues, I must say that history does not show them in a good light. Whatever piano pedagogues have said in the past 280 years has been rejected by the next generation of pedagogues. Meanwhile a minority of pianists kept playing superlatively well disregarding whatever was the pedagogical dogma of the day.
And by the way:
Apparently many pedagogues agree with that
Are you saying that 100 000 lemings cannot be wrong?

It is wonderful that you have a system that works great for your students, and it's fine that you have your opinion on this, but you came across with a bit of "my way or the highway" attitude. I like to read ideas here without getting the implication that I and anyone else with different ideas are "wrong". (a la lallasvensson) 
I don't quite know what to make of this paragraph. I certainly cannot control the way I come across. This is printed words. The model of the model. As such words can be interpreted in any way by anyone. I cannot control what implications you may choose to make from my posts. Nor can I write in a way/style that will guarantee that someone will not derive some negative implication from it and get upset.
Besides it is not "my way". It is one out of many ways.
When people ask the way to somewhere I try to give directions if I have been there before. You may notice that there are many threads where I will not contribute at all because I feel that I cannot say any thing useful, and instead I will read that thread with great interest.
When I do contribute by suggesting a way to somewhere that is all that it is: a suggestion. There may be other ways, both longer and shorter, easier and harder. There will be also wrong ways that lead nowhere. And it is well possible that you have invested many years pursuing a completely wrong way (I certainly have).
So why do you resent the implication that you may be wrong? Is yours the only or the best way? If you are wrong you are wrong. It is not a big deal, and nothing to get upset about. I should know, I am constantly wrong and I don't get all uptight about it.
The question is, if you are faced with a way that implies that the way you have been following all your life is wrong what are you going to do about it? Are you going to get upset, or are you going to try it out and check if indeed it is a better way?
Please, do not misunderstand me: I offer these thoughts in a friendly way, and I would like to remind you that no one is forced to do anything that I suggest here. That is all they are: suggestions.
If you think of a better way, post it, the person who originally posted the question may benefit from having a variety of strategies to choose from. And I may have something new to experiment with.

If you only have one strategy you are stuck, if you have two strategies you are confused. But if you have three strategies, you have choice.
Best wishes,
Bernhard.