I wouldn't be quite so sure. There is an extra tph between Wolverhampton and Stafford in the new timetable, meaning that there would probably still be 2 non-overtaken itineraries per hour from Birmingham to Liverpool. Obviously not as convenient as a through service if you have to change, but if it's somewhere like Stafford then it could even be scheduled as a same-platform or cross-platform change.
Such a change is already commonly recommended by journey planners for passengers heading from the Trent Valley semifast to stations Crewe and north. It's even announced by the station staff manually whenever the semifast arrives, indicating quite how many people use it.
Yes there is a big market from the likes of Milton Keynes, Rugby, Nuneaton to Liverpool and the TOC itself would love to extend to Liverpool or Preston but The bidding only included the allocation to the franchise bidders of 2 paths between Crewe and Weaver junction so unless this was relaxed a 3rd tph between Crewe and Liverpool would have to be routed via Earlestown. This is where this Manchester Airport plan came from