Then the design is going to be restricted in it's use. You are consigning it to a limited market.
Yes, that's basicly the trick. One aircraft that can do it all is an inherent compromise. On shorter distances (e.g Europe) you pay a high price for this flexibility. With fuel prices approaching 35% of total airline costs it is becoming no longer acceptable for the operators.
The NB market is so big dedicated types for various markets will probably be a smarter solution. So no 1-1 replacement, but a split. In the narrowbody market we allready see the Superjet, CSeries, Embraer 190/195, ARJ pushing out the heavy 737-600-700 and A318/319 where the payload range capasity of those types is not needed.
1200 NM ranges from MIA, JFK, AMS, DXB and PVG.
Luckely people live together in populated areas. Even in China most traffic is concentrated around the East Coast. Ghuanzou is little more then 1000nm away from PEK. Inbetween most activity seems concentrated. A320/737s could take care of longer / cargo included flights.