In Micheal's flashback, he writes on the paper that it is a "Bold New Plan" implying that it had never been thought of before.

In addition, the existence of Mindy St. Claire can be explained away if you assume that she was one of the architects acting like a human, like the people in the good place other than the main four characters, which she very well could be.

Anyway, that's just my hypothesis and I haven't watched past the season 1 finale yet because that's all that's on Netflix