Wow that is a beautiful quilt. I don't think Mom will notice. I know what you mean about a German woman's perfection!! You can always tell her you wanted to test her. Just to make sure she was still as sharp as ever!
You certainly can leave the blocks alone. I would not try to take it apart as you might mess up your measurements inserting a new block and find yourself in more of a pickle. You probably are a perfectionist just like your mom. At our "mom's knee"...that is where we learn. Good luck with whatever you decide.