The WCML is perfectly adequate for that. HS2 is a vanity project for business and general passenger travel, none of which is certain or impossible on the WCML already.

But the WCML is at capacity, so it is not in fact adequate.

"There is no available capacity without significantly impacting performance and causing a reduction in timetable resilience due to the resulting requirement for successive services to run on minimum headway"

https://www.orr.gov.uk/sites/default/files/om/wcml-capacity-...