Split Brain Administrators
I would use a server level trigger on CREATE DATABASE.

Something like this:

CREATE TRIGGER [CreateDatabase_OwnerMapper]
    ON ALL SERVER 
    WITH EXECUTE AS 'sa'
    FOR CREATE_DATABASE
    AS
    BEGIN

    SET NOCOUNT ON;

    DECLARE @DatabaseName NVARCHAR(128) = 
    (SELECT CAST(eventdata().query('/EVENT_INSTANCE/DatabaseName[1]/text()') as NVARCHAR(128)));

    DECLARE @SQL NVARCHAR(MAX) = '';
    SET @SQL = 'ALTER AUTHORIZATION ON DATABASE::' + @DatabaseName + ' TO sa';

    EXEC @SQL;

END


This will fire off a trigger to automatically change the owner whenever the CREATE DATABASE command is issued.

You could grant the db_owner yourself with the trigger potentially. I do this on our debt environments.