If you want to write fiction, this isn’t the place for it. It was about one thing, and ONLY one thing: national sovereignty.
That’s was the CSA states’ sole legal basis for secession, and the federal government’s legal basis for* invasion*; that is a simple fact, and if you deny this you are simply wrong.
Everything else is irrelevant.
Accordingly, the South was correct in its assertion, while the federal government was 100%* wrong*. There was never a single nation-state called “The Union,” as Lincoln claimed.
EVER.
The Constitution was ratified by 13 sovereign nation-states, not one; and they didn’t unite as a single nation-state, as revisionists claim.
You can deny history, but you can’t change what happened; it just makes you the worse.