Regarding the width of the island platform at Northwich.
In my opinion, although it'll need trackwork changes, it would be best to use the existing platforms for any Middlewich/Sandbach services. Get rid of the third and fourth tracks behind the westbound platform. The platform can then be relatively easily widened if necessary and a ramp built for DDA requirements up to the road bridge on the land vacated by the old tracks.
Alternatively the platform could be widened by removing the third track but retaining the fourth track and building the extra width where the third track was. Not as easy to get a ramp in though.
Google earth shows where the third and fourth tracks are...
https://www.google.co.uk/maps/place...3b2c28f94a620a2!8m2!3d53.2586803!4d-2.5181321