In one of the original pilot episodes, Mrs. Roper is wearing a pantsuit, which means that someone must have decided thought Mrs. Ripper’s wardrobe needed to be different.

It was the mid 70s and I think they tried to make her eclectic. Did she not also have tinted glasses on in one of the pilots? To put it in perspective, these pilots were filmed around the same time as the Brady Bunch variety show. Look at those crazy mid 70s costumes.
I saw an interview with Norman Fell and he said he sort of dressed and created the Stanley character. It was written that he was a nervous geek with a suit and tie. He made Stanley more relaxed and added humor to the character. Maybe its what Audra did to her character too....adding some personality to it.