What if a bigger change in the old ships giving them SCO optimization would be the story and lore background of ship interiors, which would require quite some remodeling of a lot of ships ?Not really. The story behind the new ships is that they had to be designed from scratch for optimised SCO, with improved thermals and sturdier structure.
Many of the original ships are several hundred years old; the adder design is from nearly 400 years ago.