There are lots of issues with this expansion. I have not read anything about the rest of the infrastructure required to support large aircraft. I doubt the Ramps and taxiways will support the weight of 737 class aircraft. Currently most aircraft don't fuel there however large jets will have to fuel as they can't land with excess fuel for the return leg. 5000 gallons of fuel per flight would be a average. 10 flights a day would need 50,000 gallons barged in each day. You need extensive storage facilities for that fuel. Take a look at the tanks at STT next time you are there. The current price for Jet Fuel is 5.50 a gallon at EIS. Airlines are paying about 1.50 a gallon in the US right now. Even with the big discounts airlines get I suspect the price would still be 4 bucks a gallon. That's going to add a large premium to fares.
If this runway does get built I would expect departure taxes to rival the UK approaching 200 dollars per passenger on top of the fuel premium. You won't see any bargin airfares out of EIS.
G