this is in my point of view a usability question or perhaps a feature request.
When a thing is deleted, this is not propagated to the items. So you have to delete the items manually before or after deleting a thing, with the risk of accidentally deleting a wrong item.
Also, if I deactivate a thing temporarily, the related items still show up in the overview pages. This makes not much sense, because for example in case of a temperature sensor, the displayed value is void.
The question is, what is a convenient way for the average user? And such a user would expect items to be hidden if the thing is disabled or items to be removed, if the thing is deleted. I know there are exceptions where you wouldn’t like to have this, but you would solve this for example be making the propagated deletion optional.
How do you think about this?