Hi @mikebar,
Welcome to the Auth0 Community!
As you wish not to utilize our Organizations feature, one workaround that I could suggest to ensure user separation would be to create different Databases and take advantage of Role-Based Access Control. While I do agree that this is a tedious process, it can achieve the goal that you have in mind.
With RBAC, you can configure different Roles ( Coach and Player ), establish each role’s permissions and then separate each team in different databases, which will work in tandem as RBAC is tied to the API and not the DB.
As you’ve mentioned the behavior of sending the users an invitation email to register, you can create separation per DB/Connection within the invitation itself and direct a user to a specific DB. You can achieve this with the Management API’s Create a user endpoint. More information can be found on this Community Post as well, even though it mainly tackles the subject of Organizations.
Hope this helped!
Gerald