I read a letter in a recent Aviation Week about suggestions on how to improve the 717. First of all, Boeing is going to use something called the "Toyota Rail System" (or some such thing) to speed up the 717 production line. Airlines have been getting better than expected performance results from the 717, such as increased fuel efficiency. But the plane can be even better. Check it out:
Why doesn't Boeing change the rudder hinges on the 717? The current rudder hinges were inherited from McD, but Boeing has produced a more efficient rudder hinge system for the 757/767 and other aircraft that would reduce drag, and decrease fuel burn rates further, and increase cruise speed and range.
Also, why not add winglets for improved fuel consumption? Boeing has experience building aircraft with winglets with the B747-400 production line and the 737-800 blended winglets. Of course I wouldn't wish the latter on a beautiful plane like the 717, but small winglets might make the plane more fuel efficient.
Now if Boeing has the ability to do this, and are building the 717, why not make it "all that it can be"?