In 1865, a lot of people were still unsatisfied with the blood-stained banner, even though few examples of it actually flew in OTL. The St. Andrew's cross canton based on the battle flags was already overwhelmingly popular and well regarded, and it went on to be the basis for the "rebel flag" that we still (don't) love. Could that have actually come to be the CSA's national flag at some point? Or would it have remained the canton for some other design?