Last week i travelled on the 1715 from Manchester to Glasgow and it was packed (4 car 350) i got on the first carriage and most seats had a reservation label and communters piled . Luckily i got a seat after preston . Edinburgh seems to get the 8 car 350s so i think a service at peak time from Manchester deserves better . An idea could be Virgin running Euston to Glasgow via Manchester or omitting Preston on this peak service !
You need to complete the current ICWC franchise consultation to get this idea registered.
https://www.gov.uk/government/consultations/future-of-intercity-west-coast-rail-franchise
Actually there's no sign at all that DfT has anything in mind for the next franchise other than tweaking the current timetable with the existing stock.
To achieve anything like you suggest, ICWC would need more stock, something the DfT keeps on avoiding (because it is looking ahead to HS2).
To get current VT services you can always go from Manchester via Warrington, Wigan or Preston on VT & Connections fares, or walk-up fares (SVR etc).
It's only TPE Advances which restrict you to their 350s.
There is a VT-only fare, but you could only do that via Crewe; however no trains are offered as far as I can see.
Another thought is that most WCML tickets to Edinburgh are valid via Glasgow (but not the other way round), so you could get VT to Glasgow and reach Edinburgh on SR/XC.