Sounds like you're talking about the East Apron and the that apron was widened to be able to accept 4 aircraft up to A321's (instead of 3). The parking points are offset to allow the aircraft to be parked "so close" together. I don't believe the airport are limiting the aircraft they can handle because the size of the stands suit the operators and I don't believe there's any plans to go into a market where bigger aircraft sizes are needed.
As for congestion 1430 can be a particularly busy time but there's never been a one way system in place as such, aircraft will push and taxi in the most expeditious way whilst balancing the delay against the inbounds. The Ops centre do a good job at stand allocation so that when aircraft are due to be ready they are spread around the airport to limit scenarios where aircraft parked closely together are ready at the same time however as soon as one or two aircraft are delayed that plan can go out the window.