Well if you are going to slap some wings on, then may I suggest some other "slap-ons"?
1. Newer efficient engines
2. A whole new bleed air system that will sustain environmental, pressurization, anti-ice, requirements that dont come off the engines?
3. A whole new system for flight control movement that does not utilize conventional hydraulic systems, assoc. plumbing and servicing.
4. A lot more composites and less alloys used in airframe, wing construction.


When you finishing being slappy, then and only then could you start waving goodbye to the regionals, but a wing alone does not make a 787.