Changing geometry in linked duplicates I have a parent object with numerous child objects and made also a bunch of linked copies (via alt+D) of said parent object inside my scene. 
As it turns out, I need to merge the child objects into the mesh of the parent object now and was wondering if there is a way to accomplish that without breaking the link to all the linked copies and basically propagate the same change to all of these linked copies.
The problem is, that memory usage of the scene would just explode if I loose the linked duplicates.
Let say the object A has a lot of linked duplications, and object A has a mesh called A'. Let say you have a B object with a mesh called B'. You want B' to be part of A. If you select B object, then select A, then ctrlJ, the A object is now made of the A' + B'. All the A linked copies are now made of A' + B'. It won't explode any memory as a linked duplication doesn't weigh on the file.

Now, if B was also linked duplicated and you need to delete all the now useless copies of B (considering B' is now part of A), you can select one of the B objects and press shift L Select Linked > Object Data and it will select all the Bs. Then X to delete.

Does it answer?