AutoCAD Inventor :: Adding Part To Single Level Of Detail

First, is there a way to add a new part to an assembly and it only be added to the active Level of Detail (and the Master, of course)?  It is adding a significant source of potential error when adding a part to an assembly when you have to make sure to go back and change the status of a newly added part in each Level of Detail.

Secondly, is there a better solution than using Levels of Detail in the first place?  We typically have assemblies that are in a few stages: 1) an empty shell 2) shell with ballast 3) shell with ballast and fill material.  I have started using Levels of Detail to suppress components at each of those 3 stages because it is important that we have accurate weights for each stage.  Our assemblies are not terribly large so memory usage is not really a problem, and I have read on Levels of Detail it is usually useful in a memory management situation. 

Lastly, is there any good reason to not be able to save a Level of Detail when there is a positional representation active?

Inventor 2013 (SP2 Update 2), Windows 7 Professional (64-bit), SP1, Intel Xeon 3.07GHz CPU, 12GB RAM, NVIDIA Quadro 2000, Vault Basic 2013