Yes, I agree this would be very helpful. By having an option to select a relative field (e.g., matter.attorney) as the "Owner" of a task, the system should be able to update who the task is assigned to, particularly when the matter is reassigned to a different individual (e.g., the Attorney of the matter is updated to a different person). Without this, updating the "Attorney" field of the matter does not (and will not) update owners of any Tasks, so it's necessary to change them separately.
This seems like a very easy change and is really important.