I think your referring to them as 'equal and sovereign nation-states' badly exaggerates their status. They were neither nations or sovereign, and never were intended to be. But I agree completely with you that they were all equal. And as equals then it stands to reason that some states cannot on their own declare that the compact is violated and leave at the expense of those staying. I believe the Constitution protected all states, those wanting to leave and those wanting to stay. And in light of that I can't understand how someone can say the Constitution could be used as a club by those states wanting to leave to beat those wanting to stay. It just doesn't make sense.
...nor do I believe that many of Lincoln’s actions (i.e., suspension of habeas corpus, arresting the elected officials in Maryland, consolidation of federal power) was anything the founders had envisioned or would have approved.
Again you badly overstate the case. Lincoln's action in suspending habeas corpus may or may not have violated the Constitution. Since the Supreme Court has never ruled on the question then we can't say for sure. As for the Maryland legislature, treason is treason. The South was engaged in a bloody and violent rebellion against the U.S., a rebellion they themselves started. Some members of the Maryland legislature were advocating joining that rebellion. How can anyone not look upon that as treason? And your vague claim of 'consolidation of federal power' is hard to debate without any specifics.
2) Lincoln had reporters arrested and newspapers shut down during the war.
3)Lincoln arrested the duly elected officials of the state of Maryland and replaced them with those he knew to be sympathetic to him.
4)Lincoln had dissenters against the war arrested.
5)Lincoln defied an order from the Supreme Court and ordered the Chief Justice arrested.
6)While the Supreme Court never ruled directly on Lincoln's suspension of habeas corpus, ex parte Milligan forbade the government from trying civilians in military court, as Lincoln's administration had done 10,000 times...
I understand that the Articles of Confederation is NOT the Constitution, BUT the Articles state—“Each state retains its sovereignty, freedom, and independence, and every power, jurisdiction, and right, which is not by this Confederation expressly delegated to the United States, in Congress assembled.” This is the status they held PRIOR to joining the United States of America via the Constitution....why would they accept a lesser status to ratify the Constitution? That makes no sense and gives them no benefit.