Please add another attribute to all objects that specifies the base point which is modifiable using a ruler helper for subsequent transformations. For example, making a crown or ring gear using the smart duplicate feature or rotating a flap around a bearing (like a water wheel). The user should be able to double-click that "pinpoint" to reset it to the center-middle of the object. These additional point locations should be saved in the file so you don't need to re-establish them every time.
Set Pivot point for rotating and/or transforming