1. Pride causing politicians to refuse a compromise? Would not be the first time.
2. If France has a role in supporting the CSA against the Union in negotiations what would stop the CSA from selling supplies to the French after the armistice/treaty?
3. I'm not ignoring anything, two of their states looked like they were interested in joining the CSA and at least one more was entertaining CSA representatives.
4. Lincoln gave Young all but written permission to ignore much of the anti-bigamy and other contra-Mormon legislation passed in the days following the Utah War and 1860 elections. Utah was under a military occupation for a while prior to the Civil War and I find it likely that they will at least inquire about taking the Utah Territory independent if the CSA breaks free.
5. Or they might use Maryland as a reason to solidify claims elsewhere. The CSA claims MD and holds at least some of KY, IT, NM, AZ, and MO while holding tacit legal rights to the lowermost Delmarva peninsula. The Union claims every part of the CSA but does not hold the region and most of West Virginia is still in CSA hands. Negotiations will commence, and I think that MO, AZ/NM, and KY will be offered plebiscites, IT goes Confederate while Delmarva and MD stay in the Union.
*Again, we're talking about a subjective "best possible", and while Tunguska wiping out the Union leadership would make for a dark/interesting timeline, I think a Trent intervention is the best chance the CSA has as it stops the fighting before the industrial might of the USA can be brought to bear.
1) Are you completely unfamiliar with the character of Lincoln? His interactions with Congress, the Press, his Cabinet, and his generals repeatedly show Lincoln as a man who did not let pride get in the way of the good of the country.
2) The CSA does not have a surplus of grain, vegetables, livestock, clothing, boots, blankets, tents, horses, saddles, tack, wagons, arms, shot, powder, medicine, or tools. In many cases, the CSA don’t have enough for their own people and will have to import. The only ‘supplies’ the CSA has to sell to France are tobacco and cotton.
3) You are flatly and repeatedly ignoring the actual actions of the actual people in the actual Mexican states, who violently resisted foreign control by a non-slaveholding Catholic country. Only
one Mexican suggested joining the Confederacy. That’s it. One man compared to the thousands of Mexicans you repeatedly ignore.
Two more Mexican governors did meet with Confederate diplomats, but joining the Confederacy was never discussed. One governor rejected all Confederate proposals. The other rejected every proposal except trading with the Confederacy, even then he refused to take Confederate currency.
4) Who is this mysterious ‘they’? Give me one man, any man in Utah, who advocated Utah seceding from the Union.
5) The Confederacy has no chance of obtaining Maryland, Kentucky, West Virginia, or Arizona on the battlefield. If they’re extremely lucky, they might successfully seize southern Missouri, but they’ll be lucky to keep all of Tennessee and Arkansas.
The Confederacy will only gain land at the negotiating table if they cede something they control. The CSA cannot offer enough to get Kentucky, or Maryland. The CSA might be able to get the rest of Arkansas if they cede the rest of Tennessee, or vice versa.
There will be no plebiscites. In a fair plebiscite Kentucky and Missouri will stay Union, but after Bleeding Kansas, Union negotiators be idiots to trust the Confederacy in a plebiscite. For that matter most CSA states never held a plebiscite on secession, even though many of them were supposed to, so Confederate negotiators probably won’t want to bring the subject up.
I could understand your thinking a Trent intervention would produce the best victory for the CSA, but that’s not what you’re suggesting. You persist in giving the CSA states that they had no chance of persuading to join them, guaranteeing decades of internal unrest from Union and Mexican nationalists, totally indefensible borders, and two large hostile neighbors with every reason to ally against the Confederacy.