Slowhorse,
Horses are balloted in the Cup relative to the WFA scale so the VRC obviously have disagreed with you for many years.
The only Doncaster winners since 1970 that I can recall with 58+ besides Sunline are Gunsynd and Super Impose - both all time great milers. There haven't been "plenty".
My argument re Northerly is this. Many Sunday experts were crying that Sunline was thrown in to the Doncaster with 58 - presumably they were sour grapes having backed something else and not the "lightly" weighted mare. Surely a horse with a great WFA record like Northerly is well weighted with 58 when a horse like Central Park with moderate European form could run a close second with 57. Vintage Crop sat 5 wide as a 9 year old with 59 or 59.5 and ran third. Super Impose ran 4th with 60 and hadn't won a Cox Plate at the time.
The big weights aren't carried to victory often in the Cup because they don't try. A quality galloper with a reasonable weight such as Northerly should be competitive against what will essentially be a field of handicappers and plodders.
Northerly will only compete in races up to 2000m prior to the Cox Plate over 2040. The Cup is only 10 days later and the only other suitable lead up would be the McKinnon, again 2000m. I believe a horse must have a 2400+ under its belt leading up to the Cup. It is pretty clear Kersley is not Cup bound.
My question is why not.