There are a lot of people who can do mystery quilts. I am not one of them. I did do one. If I had known how it went together I would have chosen a different fabric for the center (it was a medallion quilt). I decided once was enough.
Scrappies I do like. The first few were controlled. The last 2 were "pull out of the bags" - one lights, one darks. They actually do not make me uncomfortable anymore.
We all need to "let go" on occasion but I like to chose when I do that. I sometimes make up my quilts "as I go".
Based on your directions I have no clue what it could be. Good luck. Hopefully it will turn out well for you.