[steam for ever]

Well Tony I still think that a refurbished Central station would be great, but the more Metrolink get their fiddling hands on the area the more difficult it will be.
In order to use the approach viaduct, a link viaduct will have to be built or somehow cross the metrolink lines by means of tunnel or over bridge, so either way Mayfield would be cheaper.

One of the reasons for building Hs2 is to relieve the WCML, so any traffic would be local in theory.
If a feasable way to get Hs2 into central station can be found, I'm up for it, and will back them all the way, but building a whole new line to link with the approach viaduct will involve demolition of a large portion of south west Manchester. Apart from linking with existing lines it can't be used.

If however, central were linked to exisiting local lines, this would relieve the WCML to a suitable degree to cope with Hs2 sharing the line.

So ideally, reopening both stations for different uses would create a good balance.