Oh forgot to mention: The part shown in the penultimate picture was created with the correct texture on both sides, so that the inside view is also correct.
I would not name it add-on kit, but I would upload my parts to this model. Maybe it might be used as is or as a basis for better parts.You are doing a great job on this project! I like your solution for making a more "accurate" version of this model.
Are you planning to make an add-on kit for this model?