I dunno if this is even possible, but could EI perhaps use narrowbodies over the Atlantic, they would probably need ETOPS certification, and perhaps auxilary tanks?
If using an A320 they get 174 seats(prob less cause they would pob need a premier class service, or in the region of 210/220 on the A321s? Surely the systems for auxilary tanks is very similar to the 'snap-in' type on the a319LR? It would just provide a graduated increase in capacity as t/a service is introduced, in fairness the yanks, if they ever come, will prob use 757s any way!