Note platform length is 82.5m.
Mt. Pleasant Station / VGH Oak Station / South Granville Station / Arbutus Station
These ones have Concourse Level knock-out panels to the north and south,
though the ones on the same side as the main station house seem to be too close to be of any use
since they lead to a fare paid area and faregates would have to be installed in a secondary entrance.
There's a general design element where secondary access points lead to the Concourse Level,
which may overload use of the same escalators from the platform.
I suppose they may also be able to add an exit at the opposite ends of the platform as well through what are the emergency exit areas, but we don't know if "service areas" are occupied by huge ventilation fans that cannot be relocated to enlarge passages.
Broadway City-Hall Station
The consultation materials fail to show the "Mezzanine Level".
The 2nd dagram is called Concourse level (not Mezzanine), and a cross passage to the northbound Canada Line platform is not shown.
I think the passage shown is to the southbound platform.
This one also has Concourse Level knock-out panels both north and south.
You can see the missing level here.
That's quite the oversight for consultation purposes as it omits display of a platform cross connection.
At least the plans look consistent with this diagram.