Is there a strong case to reopen the line?
I doubt it, Warrington already has 2 direct links to Manchester. It would also have a potential impact on Arpley Sidings, as the line down to the viaduct is used as a headshunt or runround loop, I think.
Most, if not all, of the route and its structures are still intact and Lymm especially would benefit greatly from a new rail service into Manchester, and to Warrington.
Unfortunately, at Altrincham there's a rather large business park very firmly over the top of the old route. There also looks to be obstructions at Lymm. And in the eyes of the planning people, the old structures and route will mean very, very little. It's a new-build line. W12 gauge is almost certain to be required (Latchford viaduct, if it could be retained, may get an exemption).
The viaduct over the Ship Canal at Latchford probably needs a bit of work doing to it, but it doesn't look in a terrible state.
Depending on what you want to carry it could need anything from a sand down and repaint to total replacement. I suspect it will need a fair bit of work as this line would have potential for freight traffic, and therefore would probably be built to RA10.
But the biggest problem, by a very long way, is where do the trains go once they've got to Warrington or Altrincham? There's no more space through Stockport and you'd want to run beyond Warrington to Liverpool, and Lime Street isn't the quietest place in the North West.