Look you got a simple task.
You would want to add a simple ViewRow with custom content. It should be ultra easy like in other frameworks right? Wrong! Because you need existing entity. You cannot modify it because you need to display existin gentity also. You want to alter view to add non existing records (like empty records for each user) but you can not without using solution that take longer that writing custom controller by yourself.
Same goes for Drupal Commerce, perfect solution for problems that does not exists.