Merlin, I have to confess that I disagree with a number of the points you have made.
In an earlier post you said that it was not necessary for an independent Scotland to have a separate coronation (presumably, if the Scots accept that England and Scotland have the same person as monarch).
I think that most accept that Queen Elizabeth II is currently Queen of Scotland. The question of a separate coronation for (and in) Scotland could arise with the next monarch - depending on whether Scotland votes for Independence and a separate coronation. I think it would be disastrous, politically and for the British Monarchy, if a subsequent British/English monarch refused to take part in a Scottish coronation.

In your post above you stated: 'This singularity extends also to the function of The Queen as a focus for all her peoples: she is the Anointed Sovereign and wears the Crown of all her peoples. This unity includes the peoples of the nations that have chosen to recognise Her Majesty as Head of the Commonwealth while having their own Head of State.'
I could dispute your statement on many levels - but I will try to keep it to the issue of monarchy and the significance of a British coronation for the Commonwealth. I think there are a number of pertinent issues.
First, while Queen Elizabeth, as the Monarch of the UK, is currently a unifying symbol for the Commonwealth of Nations, the next Head of the Commonwealth of Nations does not have to be the monarch of the UK.
Secondly, have you considered that within the Commonwealth of Nations there are other monarchs of independent nations? I think that negates your comment that HM 'wears the Crown of all her peoples'. Or - are you suggesting that they are somehow lesser monarchs than the monarch of the UK? The world and the political scene (v a v former colonies) has changed radically since the coronation of Queen Elizabeth. (I will accept that some monarchs rule nations with less political clout but that, in my opinion, is not a reason to view such monarchs as not equal to QEII)
Another aspect which interests me is that, as far as I know, the other monarchs within the Commonwealth of Nations are not Christian.
Earlier you stated -'For one country within the Commonwealth to stage a 'coronation' because of what it may have done prior to its unity in the indivisible Crown could be regarded at best as a Nationalist mockery and at worst as a blasphemous pantomime.'
I do not understand why you consider the Crown as indivisible? The Union of England and Scotland was political, created by legislation and so it can be separated by legislation. Any nation within the Commonwealth of Nations can opt for a non monarchical system - so as far as us former colonials are concerned, the Crown is not indivisible.
As I do not understand matters could you explain why having a separate coronation in Scotland in the future (assuming that the Scots accept that the King/Queen of England is also King/Queen of Scotland) could be considered blasphemous?