The journal idea is great for individuals, as a journal is your story. I believe this would be very hard to do as a BOM as everyones story is different. The idea behind a BOM is that everyone makes the same quilt design with their own twist, month by month.
I see nothing wrong with starting a journal quilt as a group project - not a BOM - where you can ask other quilters for suggestions and patterns - ending up with 12 blocks.