When device type is deleted remove related objects
This would help customer mange many device at one time. For example customer has 1000 child devices of one device type and after some time this device type is no longer supported. Customer has to manually remove 1000 child devices and he has to be aware which devices have this device type. This takes lot of time and effort for the customer. Expected behavior would be that once device type is deleted to remove all related objects or to provide user with possibility to select that.