Should volume be a hard limit when designing vehicles? Are there occasions when it should and others where it should be treated as a guideline?
Marine Vessels: for pure water, 1 cubmet = 1 metric ton, so a marine vessel needs a higher volume to have buoyancy. These also applies to subs, they are built as low riding surface vessels so that you have buoyancy tanks. So for a marine vessel, a higher volume is preferred, but stability issues may require a limit at some level.
Aircraft: Mass is the main limitation: the higher the mass, the greater the cost to get it airborne. Volume is only limited by the needs of streamlining to reduce drag.
In fact, for most vehicles, mass is the primary driver of the design. Volume seems to be most often impacted by external requirements, such as the width of a lane on a road.