Everyone knows that the Confederacy was that evil part of the country that saw no problem with owning people. But it wasn't all bad, especially when it came to their Constitution.
If you read the Confederate Constitution, although most of it is copied verbatim, there are several areas that differ significantly from ours. Slavery, of course, was made legal subject to the same limitations on importation of any new slaves. But a separation of State and Economy got the most new changes and limitations on the government.
It explicitly banned their federal government from favoring any branch of industry in any way via duties or taxes on imports.
It required a 2/3 vote for approval of federal appropriations outside of a limited list of purposes as well as for taxes or duties on exports.
It required appropriations to have specific line item amounts for specific purposes and banned any additional payments to anyone after the initial contract had been made or services rendered.
It gave the President a line item veto on expenditures.
It most forcefully banned Congress from appropriating any money for the facilitation of commerce aside from a very few specific cases involving water transportations such as buoys, lighthouses and dredging, and, even in those, duties were to be laid on the navigation that got those improvements until they were paid for.
It made the Post Office pay for itself after the first two years.
It also made a Constitutional Convention easier to call for, requiring only three states instead of our 3/4. It limited the number of people any one Representative in the House could represent to 50,000. It gave the President the power to remove any department head or anyone in the diplomatic service. It also incorporated the Bill of Rights almost verbatim into the Constitution itself.
One of my favorites was getting rid of general omnibus bills: "Every law, or resolution having the force of law, shall relate to but one subject, and that shall be expressed in the title."
Except, of course, for the issue of slavery, I approve of almost all of them. They were almost all additional and explicit limitations on the power of the government in areas that our Constitution over the previous 70 years was found to be lacking in actual practice. Of all of the changes, only the slavery one was changed in ours.
Lincoln's issue, the succession itself, has never been addressed. There never was any ban on it. In fact Texas, which used to be an independent nation on its own, explicitly wrote into the agreement when it joined the US that it reserved the right to secede.