Jane,
If gamepieces are too similar from year to year, existing teams have another edge over rookies in that they already know how to build a manipulator that would work with the gamepiece. Or, conversely, know what wouldn't work.
Having an oddball piece (like tetras and ringers) puts teams back on similar levels; no one has had experience with that piece.
Since we had a ball year this season (even though it was a huge ball!) we're "due", by some people's figgerin, to have another oddball piece next year. Having fun trying to guess what that piece will be is like trying to guess what a certain curmudgeon's hints mean. Maybe it's time for bananas or fish!