unfortunately I can´t help you with that question, because I´m no expert in WWI. My information about the saxon regiments comes from a list from 1900. I can only tell about the 5th army from the memoires of Prince Wilhelm.
-V., XIII., XVI. A.K., V., VI. Reserve-Korps (Posen and Silesia), 13th (Province Saxony), 48th (hessian), 45th (saxon), 53th (württembergian) and 9th Bavarian mixed Landwehr Brigade, Mörser-Regimenter 6 and 12, Engineer-Regiments 20 and 29, 5th and 6th Cavalry Division. I should mention, the Landwehr brigades had no regimental organisation. What you have is only peacetime organisation, which changed a lot at war. Maybe that helps a little.