Joel~
I understand what you might have against configurations, but I
think in this case they are the way to go. To my knowledge the
explode line sketch is one sketch, and I am not aware that you can
hide part of it dependant on a display state.
The way we handle this situation is to use derived configs, making
sure that the option to suppress new mates and new components is
selected. This way you don't get surprise additions in the derived
exploded view. Then we suppress the items we don't want to show or
appear in the BOM. Alternatively, it is possible to show a
component and in its properties select "Exclude from Bill of
Materials." This setting is specific to the configuration so it
won't affect your master config BOM.
Hope this helps.
Joel~