Db_owner VS Db_ddladmin Roles

We have several departamental "database administrators" that needs access to their databases "only" and cannot perform maintenance tasks administrative tasks such as backup and create new server login. We basically function as a "database hosting services" to these departamental dbsa. I granted rights to these departamental dbas to their database and I assigned the db_ddladmin role to them. They can create the objects within their database but they cannot read the records because when the table was created it belongs to the dbo schema - I don't want to assign them to the db_owner role, this role is much more permission that they need.

My question is: What is the best way to give these departamental dbas rights to manage their databases without having too much permission to maintain the database permission and settings?