It's not the position that breaks down. It is the political reality. The difficulty is with perceived violations and grievances. What seems to be unappreciated by those who take your position is that the perceived grievance must be very significant to wish to commit to so dangerous and difficult matter as to break off. Indeed it is possible that those who broke off 'broke covenant'. True, and that, my friend, is the entire problem and the reason for this debate. Practically speaking, if consent of all is required, secession is never going to happen. The alternatives to my position are only these: chaotic revolution or enforced union. Therefore, the Framers never included in the Constitution requirements for secession.
Regarding your statement about the 'creation' of new states. It is the people of each State who create each, the US acknowledges their existence and admits them with the same standing as the other states. That is why I used the word 'principle'.
To conclude, on your side, you do not fully recognize the sovereignty of the state (or rather the people in each state). Now I don't demean the Constitution as a mere treaty. However, if the violations are severe enough and irreconcilable by other means, secession is not a mere option but a duty. What, then, you ask is severe enough? I respond that it is to be determined by the people of the state? The question is when do violations become insufferable? Now some will suffer more, some less. As for individuals, so too with state's. That is why I prefer to leave it entirely to states. Of course, I consider it unlikely one State would secede on its own.
Part of the reason I continue this discussion too is that I've also been considering other obstacles and implications in secession, which is good at least to consider even a little, if not thoroughly.
“…the perceived grievance must be very significant to wish to commit…”
The perceived grievance may be very significant but that does not make it more than perceived. It may not be real.
“It is the political reality.”
The political reality is that there will be no higher authority (as you admitted), no one else to judge, therefore your position (from post 1187 and elsewhere) “that states with equal authority cannot be judges of their own case” is erroneous as far as I can tell. There will be no one else in a position to judge. There will be no one in authority to tell them they can’t judge.
Your position that “any state can leave if the contract has been violated” is subject to the state’s ability to do so in the face of opposition.
“Practically speaking, if consent of all is required, secession is never going to happen.”
I don’t agree. If you’d said “improbable” or “not likely to happen” or something qualified like that I’d have been OK with it. But “never”? I can’t agree with that.
“The alternatives to my position are only these: chaotic revolution or enforced union.”
I don’t see how those are alternatives to your position “that states with equal authority cannot be judges of their own case”. There more like outcomes of states trying to be judges of their own case, but even that’s shaky. They don’t relate enough to your just stated position to be alternatives to it.
As to your position that “any state can leave if the contract has been violated”, I see chaotic revolution or enforced union more as possible outcomes than alternatives.
And I agree that “any state can leave if the contract has been violated”, putting an emphasis on “can” and subject to the State’s ability to do so in the face of opposition. If we replace “can” with “may” it might not make a difference.