I've seen a few suggestions for being able to select and group component parts and then do various things with said groups (copy, paste, etc.). I don't know if anyone's suggested this, though:

-Ability to click and drag single parts or locked groups of parts and "snap" them onto existing surfaces.
          -adhering the specific surface of the piece/group selected to specific surface of the piece/group being attached to
           -pieces glowing red that are conflicting with others
-Allow free-floating pieces or groups to be translated separately
-Allow saved groups to be added to an existing build (ie, so I can bring my ballista add-on to another vehicle of mine)

That's all I have for now. Feel free, everyone, to add any additional thoughts on the subject! I'll be back if I think of anything else.