Another thing in my mind about the split is how Ciel-sensei explains it as A Piece of Blue Glass Moon being the action routes and Other Side of Red Garden being the mystery routes, so I feel like Akiha and Hisui will generally be same puzzles with roughly the same solutions, just accounting for Arach and Saiki's involvement in them, Kohaku will include new puzzles and maybe resolve Gouto, and Satsuki will be the where the whole mansion plot and the whole vampire plot together will be tied together through Arach's resolution.