If money is to be spent, it needs to be a proper solution, not a fudge.
I'm not sure it's be any more of a fudge than Picc P15/16, to be honest, provided they put travelators in.
But really, the best solution remains, from the point of view of Vic, to get rid of the Arena and build a large replacement station on the entire site, something around the size of Birmingham New St with the same level of facilities. The layout of Manchester's railways doesn't (like London) really lend itself to one Hauptbahnhof, but you could at least make the two main stations vaguely equivalent in facilities.
Then (hello
@Bantamzen 
) Castlefield becomes "S-Bahn" only, potentially using only 3/6 car CAF formations and even adding half-height platform edge doors - like it was for many years before the Windsor Link was built. Operate it like Merseyrail and it won't be a problem - Liverpool Central's busy Northern Line platforms handle 8tph terminating and reversing, and 4tph through trains in each direction (so 16 train movements per hour) with very few operational problems (the problems are mostly about passenger overcrowding, not punctuality), which (because of the disruptions the reversals cause) is well in excess of what 13/14 would be handling in that scenario.
With regard to connectivity, you could also do some rebuilding at Salford Crescent and stop everything inbound there, then it'd be an easy and quick connection onto a high capacity, frequent S-Bahn if you wanted one of the Castlefield stations. Perhaps (and there is room, I'm pretty sure of it) it could be something like two through platforms (with those services mostly or solely to Vic) and a central bay with doors open on both sides (with an S-Bahn service to Manchester Airport at least 4 times an hour, with another 2 coming from Rochdale/Vic via Ordsall, and a further 2 from the CLC, giving a total of 8tph on Castlefield)?
Perhaps two or even four of those could serve Levenshulme, Heaton Chapel and Stockport (and on to Hazel Grove?) rather than overserving Ringway? And perhaps two continue from Ringway (reversing) to Crewe via Styal?