Well LGW/MAN based 4 Virgin Sun A320s didn't last very long. The Brussels based Virgin Express was short lived too.
VS operate T2 at MAN, but as far as I am aware has no domestic facility, so there will probably be split Terminal ops at MAN (maybe LHR too).
MAN pax can go anywhere westbound via existing carriers & eastbound is well served with EY, QR, & EK. Don't see the attraction of going via LHR. BAs own shuttle has fallen away over the years as alternatives have come on tap.B757 & 767s reduced to A319s etc.
Can't see any way this will pay it's way.
More of an expensive political stunt / point & a spat from losing Manchester to London rail franchise.
If he wanted to make an impact oop north ( & offer crew shuttles) then routing a Heathrow to YVR or a LAX via MAN might remotely possibly make more sense. :-)