It would need electrification and re-building the viaduct into Piccadilly as well. It’s not the answer to the problem at the moment, when in reality most people can walk the distance to existing rail services in the city. That’s not to say it won’t ever happen, just not in the next decade or two I wouldn’t have thought.
Trains are best thought of as solutions for travellers from miles away. A stop built on the Phillips Park line would need to be on a service from say, Leeds to the airport, where it has the potential to be profitable in both directions, and they would be 2 or 3 an hour. Not really suitable for moving a large number of people in a short time, and of course the route to the airport from there doesn’t currently exist, which is why trains go around the west of the city.
Terminating at Piccadilly via a new viaduct is a possibility maybe but would take decades to pay for itself. They did consider this 20 years ago before building the Ordsall Chord but it was the direct route to the airport that made them go with what they did. Re-opening Park station could be a solution but it’s still a 3/4 mile walk versus 1.5 miles to Piccadilly, it’s not perfect, but it would be on existing routes (Southport to Stalybridge, Liverpool to Newcastle) but they’re only 1 or 2 per hour.
For football though we need more frequent services and if Metrolink can’t do that it needs to be buses. I think as the land between the city and the stadium gets developed with new housing and shops, it won’t be as bad a walk as it currently is. And the Sandhills tram stop will be closer than Victoria when it’s built (1.5 miles). Then of course the facilities at the ground will soon improve for those able to hang around after the game. City Square was a bit grim before but hopefully it’ll be something very different in just 2 years. If passengers can be spread out over a longer time we might just cope with what we have. More investment in the Ashton tram line to reduce overcrowding would still be welcome though.
TL:DR
There’s lots of things to consider before splashing out mega millions on new train stations. They’re still in the process of getting buses under control and simpler ticketing and then hopefully bringing trains within GM into it. Just be patient.