Like you, I too am getting on in years. The difference between us appears to be that I tend towards the non-rail use of the Manchester Mayfield site for a new part of the general betterment of the land area in which it is so situated.
This will put cat amongst t'pigeons, but...
...if Mayfield could be made to work, the station could be integrated into a mixed use leisure/business development. There's nothing developers love more now than for city centre sites to be on or near a major rail terminus, so walking off the concourse at Mayfield, onto escalators and into Mayfield Shopping Centre would be a wet dream for many a pen pusher at the likes of Lend Lease, Westfield Corp or smaller players like Helical Bar.
It still doesn't solve the problem of how much capacity you lose on the line through Platforms 13 and 14 (and how you would ever put Platforms 15 and 16 in) if you have terminating traffic crossing the through lines at the throat to Mayfield. That's why you need a dive under or fly over, to get Mayfield traffic clear of the through lines. Tosh, of course. At grade crossings are fine and don't hoover up capacity, no sireee Bob.
The other way I can think of is viaduct extensions and using an Ardwick flyover to do all the necessary traffic separation well before the combined station throat being proposed, but that's going to be expensive, and it still doesn't provide the sort of Pic-Vic link people in Manchester have needed for decades.
Re-opening Mayfield is, to my mind, symbolic of the 'we'll just dump you here where it's most convenient for the railway' way of thinking we've tried to get rid of, Ordsall Chord is more 'we'll get you as close as we can to your destination with more through services'.