with regards to Edinburgh-Newcastle, I think there's demand for a better level of service along here than presently.
While an 'all shacks' service can't be accommodated, a semi-fast service calling at Musselburgh, Drem, Dunbar, Berwick upon Tweed, Chathill, Alnmouth, Morpeth & Cramlington, as wel as nwe stations at East Linton, Burnmouth (for Ayton & Eyemouth), Beal (for Holy Island) and Belford could work.
Additionally, the re-opening of the North Sunderland branch would give a reasonably-sized terminus for current stoppers (i.e. Manors, Cramlington, Morpeth, Pegswood, Widdrington, Acklington, Alnmouth, Chathill, North Sunderland) and would generate a good bit of holiday/day trip traffic over the summer. A more regular (i.e. hourly) service would also be much more use for commuting into Newcastle, taking traffic off the over-congested A1.
This should be possible with the introduction of loops at Cramlington & Acklington, both are which are eminemtly feasible. Giving a total service of:
Newcastle-Edinburgh (Scotrail): 1tph
Newcastle-North Sunderland (Northern): 1tph
Newcastle-Edinburgh (East Coast): 1tph
Newcastle-Edinburgh (XC): 1tph.