Surprised the B757 didn't enter the loop & then follow the A310. J2 usually "discourage" their 757 drivers from doing 180s on the runway.
As for a parallel taxiway at the 14 end: there would need to be some considerable earthworks - extending the width of the tunnel over the road for a start. Plus if Alpha taxiway at the A2 end won't take 757s there would need to be some redesign along there too by the sounds of it.
Never say never, and the allegedly up coming fuel farm move may increase the likelyhood, but I don't think its top of the list yet!