the issue i have with it IF it happens now is how long it will take to get to manchester, talk of 2040 and beyond, honestly on that time table for a lot of us why even bother, this is why IT NEEDS to be built from all three end points from the get go. would probably save them money as well as wages and costs of materials will only go up over the years of the build.
While I don't necessarily disagree with you, it's a bit late now because different parts of the route are in different stages of readiness. (the need to massively overhaul our planning etc processes to prevent the sort of obstruction we've seen on this infrastructure project is another discussion)
The only way to start from three points now is to delay significantly, which isn't really going to help.