Look at the timetables. See if you can run trains at different times. Look at running trains from different stations. Look at how technology will reduce passenger numbers. Increase the size of trains . Build new stations. Be more flexible with timetables.
There are no capacity problems on the WCML that couldn't be solved with better thinking. Just going "build a new line to Birmingham" ignores what could be done to the WCML with a bit of professionalism.
Look at the timetables - are you suggesting the existing operators don't?
See if you can run trains at different times - what does this even mean?
... from different stations - again, what are you suggesting? Do you not think the train operators don't already do this? Given the dominance of Manchester, Birmingham, Liverpool as destinations where else are you suggesting?
Look at how technology will reduce numbers - genuinely "begging the question" [i.e. assuming technology
will reduce numbers]. We have had an explosion in technology over the past 20-30 years accompanied by increasing rail usage.
Increase the size of trains - already discussed at length. Some potential, but also many difficulties.
Build new stations - where? Why?
Be more flexible with timetables - in what way? A standard hourly pattern (supplemented in the peaks) is by far the best way to maximise capacity.
"Better thinking" is just an empty slogan.