If you wanted 50/50 in situations the you would just need to rate the stars equally in a certain star category. I believe for cpu game planning and using coach suggestions (I never use this) you are limited to 20 plays they show even if you have 400 within it.
I have not had that problem not being able to tag more than 20 plays in 3rd down. In these CPU playbooks there are anywhere from 50-150 in a certain situation. I purposely did this as if a play doesn't work or CPU struggles with a play it's a easy fix by simply going in and deleting it.