It's not just about writing, though. People like alternate history in part because they want to see how historical characters react to changes. Sure, engaging OCs are possible - but they still don't have the same appeal as engaging historical characters for those readers who want to know how...
Swiss here. Just saying, the Swiss Army is a militia. We can keep our personal weapons pistol or rifle, at home. Nothkng wrong with using that system in the South after the war for loyal folks.
I think that's just part of fabricating the Lost Cause myth - lies made up to make it seem as if the South was in the right and the North forced the war on them and was unwilling to make peace on "honourable" terms.
Thirded. The whole OTL German attack was a huge gamble that paid off thanks to a lot of luck. This TL shows what would've happened I the dice hadn't rolled in Germany's favour even once or twice.
Few officers will have strategic experience, though. Most will not know anything relevant about prolonged campaigns. The average regimental commander won't be even near the level of a Prussian staff officer.
Don't forget that Europe saw a lot of wars. Sure, the officers who served in the ACW would have valuable experiences - but not really anything better than officers who served in the Crimean War, the Second Schleswig War or the Austro-Prussian War, for example.
I honestly doubt that the Japanese would have been able to invade Ceylon any more than they would've been abe to invade Hawaii. Logistics wouldn't allow either.