Then make a backup. Then restore it. I recommend restoring it on a fresh server. You can use your existing yml file, but delete USE_S3, the upload bucket and the stuff that uploads assets to S3.
I believe this could be accomplished with a single line of code. Adding it to the roadmap might be a good idea. It should be possible to switch between local to S3 and S3 to local with ease using just one line of code. I understand you are quite busy, but I think it could be beneficial in the future if you add it to the list.