1. Accountability - an elected head of state is accountable to the people, a monarch isn't
Has anyone told King Charles the first? You say this Davey but then we find this from our own Gordon
A fundamental reason for the UK, and hopefully Scotland in due course, electing to become a republic would be to remove the situation of having a hereditary head of state
So there is apparent accountability.
I was selected for many of the offices I have held because of my training I had great accountability, even to the point of being subject to criminal prosecution if I was found to have failed in my duties yet in no way could I have been said to be elected to that role and in the end that didn't matter. A king can be as accountable as that.
2. Equality - no-one should be fundamentally barred from aspiring to be head of state - determining head of state by accident of birth is a million miles from equality
And yet apparently there can be no President Schwartzeneger because he, by accident of birth, was not born in the USA. Are people fundementally born equal?, In what fundamental way are they equal? Of course there are prescriptions for this. The US constitution states that all are equal under God. Does your belief in the equality of man operate on the basis of things that are superior to humanity or what. Until you answer this you have no fundamental answer as to why a president is superior to a constitutional monarch. You have no warrant to say you have a case based on equality. There can also only be one head of state whose passage in republics has often been eased by wealth and connection.
Secondly is it logical for Democracy to be ubiquitous? I'm sure we can all think of situations where democracy isn't relevant or appropriate. And here we should not conflate absolute and constitutional monarchs.
3. Risk - you can get rid of a rubbish elected head of state, even if you have to wait a few years
Not guaranteed e.g presidents emeritus in China I believe
- you cannot get rid of a rubbish monarch without a constitutional crisis.
And of course that would be an issue in an absolute monarchy of course a constitutional monarch can be limited in what areas they can be rubbish in. Of course this is where the ''President Boris Johnson argument comes in''
4. Reputation - it is very hard for a monarch to dissociate themselves from past imperialism due to monarchical continuity and that the monarchy massively benefitted personally from aspects of our history that we feel aren't filled with glory. An elected head of state likely has no such baggage, and if they do you can vote against them.
Again Russia abolished it's monarchy and now has both a monarchical and republican past to live down, and as far as the latter is concerned, the Russian republic is having another go!. I can't see becoming a republic wiping the slate and if commonwealth countries become republics what constitutional leverage do they then have on our state?
5. Values and influence - to have influence you need to live your values - hard to argue for democracy in the face of dynastic leaders if our head of state is themselves dynastic.
Conflation of democracy, absolute monarchy, dynasty and deliberate confusion of absolute and constitutional monarchy. Might have had some traction but your resort to dodginess and sleight of hand weakens this argument. Britain is a well known example of parliamentary democracy globally respected until Brexit and the Tories. That is why the president Boris Johnson argument against a republic is so persuasive.