hi, thank-you for providing the brief history of you. As you have Flat feet, and using the shoe inserts though swelling is the issue now we need to have a thorough clinical examination and and x-ray of the lower limb. In most cases of flat feet seen in my clinical practice have suggested to understand that the body s natural mechanism shouldn t be altered and the change in the normal anatomy of the feet bones will lead to swelling . Also, since you stand static at one place for 12 hours of work, this could be required to have a vascular insufficiency which is common in many of the cases to be assessed to rule out other conditions.. Also, how is your BP, DM, Etc. as this is also going to play a role in your swelling. Having an medial arch for the feet is not a bad thought but understanding the actual mechanism and change in the normal body due to medial arch needs a thorough understanding. As body functions as one unit one should not injure other parts of the body while treating the single joint. In my clinical practice the training of the muscles needs an attention along with the medial arch for flat foot as to balance the basic requirements of the body, so we refer to physical therapy. Regards Jay Indravadan Patel