never mind the fact that every track that has a thin platform also has access to a wider one. If they really wanted to they could simply close those platforms down. only every other platform is thin.\
"Wide" is very relative. Right now, every platform is so narrow that you essentially can't get around the staircase on the platform itself. You are forced to use that staircase to access and exit the platform.
1,500 people taking 5 minutes to leave a platform currently is neither something to aspire to, nor something that translates to future operations. This is tolerable only because the train itself has a ten minute dwell time. Under regional rail operations, the train has a 60 second dwell time, and people will be waiting on the platform to board the train as people exit and snake their way through the crowd to get to the staircase. By the time people exit, another train will have arrived and the cycle will repeat itself. I mean, maybe it's possible, but I don't know a central station with serious regional rail that doesn't have wide platforms - at least platforms wide enough to build a wide staircase for both access and egress and the possibility for people on the platform to manoeuver around.
You also simply can't close those platforms down and widen the existing platforms because the concrete support structures are placed under the tracks to hold up the weight of the train. Since you can't move the tracks, you can't move the platforms.