I often create Widget Views that are based on a custom status/field (e.g. Launch) and then a specific user (e.g. Joe).
I'm forced to assign that custom status to the parent task (which i sort of get) to make sure each user can view their assigned and custom field tasks organized:
Joes Launch Tasks
Bob's Launch Tasks
In order to make this work though I have to assign both Joe and Bob to TaskA. It seems to me the Assigned Users should inherit the subtasks users. In this way all I have to do is assign users to their specific tasks and then each one could see their tasks organized by parent task/tasks.