Righto Skyman, lack of a parallel taxiway only significantly delays GA and schedules/charters are only subject to minimum delays are they?
Any pushback from stands 5 and 5R (and aircraft size/push direction dependant from 4) physically impede egress from the 'B' taxiway. Pushbacks from any stand blocks access to the 'c' and 'd' taxiways to any aircraft east of that point taxiing out. Pushbacks from any stand blocks access to 'B' and 'A' taxiways to any taxiing out aircraft west of that point.
Furthermore, unlike that which has been stated before, acceptance of the 'C' and 'D' taxiway by 737/A320 size aircraft seems to be operator dependant. Some will take it, some won't.
Let me give you a scenario.
Aircraft 1 is on 10 mile final.
Aircrafts 2 and 3 call for start and push.
All aircraft must use the'B' taxiway.
Aircraft 2 when ready can taxi to holding point 'B'. Dependant on where 1 is, 2 will either have to wait at 'B' until 1 has past 'B' on its landing roll or 1 will have to hold on the runway until 2 has cleared the intersection.
3 can't go anywhere until 1 vacates the runway and parks up.
3's delay so far is at least 5 mins.
3 taxis to 'B', by that time aircraft 4 (which also has to backtrack) is on 5 mile final. Another 7 mins delay to aircraft 3.
Aircraft 3 is on a slot time and has to return to stand awaiting a 2 hour slot time delay.
Granted this uncommon now. However, the pax no. hurdle before the parallel taxiway will be implemented no doubt will mean a lot of head scratching and, dare I say, crisis management solutions when the inevitable gridlock ensues. This scenario does not encapsulate any further deterioration of the taxiways.
Invest now for the future and let's not have the usual "Trumpton" embarassments when lack of foresight pervades.
I agree a parallel taxiway will not entice more pax through the door but once inside they will probably expect to go somewhere shortly.