Thinking out the box a little, along with the IEP's desire to have portion working (ignoring the fact NR don't want it) maybe we could have.
London services
London, York, Newcastle, Edinburgh, Haymarket stations to Aberdeen / Inverness replacing the Scotrail services.
London, Stevenage, Peterborough, York, Darlington, Durham, Newcastle, Berwick, Edinburgh, Haymarket, Motherwell, Glasgow
London, Grantham, Newark, Doncaster, York, Darlington, Newcastle, one of {Morpeth, Alnmouth, Dunbar}, Edinburgh
London, Peterborough, Newark, Retford, Wakefield, Leeds
London, Stevenage, Grantham, Doncaster, Wakefield, Leeds & Selby, Brough, Hull,
London, Peterborough, Grantham, Newark, Retford, Doncaster then onwards to Sunderland/Bradford/Middlesbrough using Grand whatevers paths.
XC would have.
Sheffield, Doncaster, York, Darlington, Durham, Newcastle
Sheffield, Wakefield, Leeds, York, Darlington or Durham on alternate hour not both, Newcastle, good spacing of {Morpeth, Alnmouth, Berwick, Dunbar}
TPE would have
Leeds, York, Thirsk, Northallerton, Darlington, Durham, Chester-Le-Street, Newcastle
Down South and extra service.
London, Huntington, Peterborough, Spalding, Sleaford, Lincoln,
I know it is impossible to cover every journey..