Re: long journey times between London and Birmingham, remember that the last time Virgin came up with a proposal for a Shrewsbury service that it was meant to be routed via Nuneaton, though I think that was supposed to be worked by 221s. Nuneaton would also offer a quieter spot to couple and uncouple 57s than New Street, never mind trying to find a path between Birmingham and Rugby - while the northbound times from Euston match current West Midland departure times, the ones heading south from New Street do not.
Stopping patterns would surely replicate old BR and W&S habits west of Wolverhampton, so, as has been said previously Cosford (W&S called here), Telford Central, Wellington, Shrewsbury, Gobowen, Chirk, Ruabon, Wrexham, Chester.
Someone asked why Cosford? Two main reasons. 1. It is home to one of the major RAF training and administrative centres, with personnel coming and going all the time; 2. W&S showed it worked as a park-and-ride for the communities between Wolverhampton and Telford, sparing people the need to drive into either place to get a London service.