I think triple has some good points on the voltage drop issue.
I will add that I am not in a hurry to see 60 circuits brought into one 14" W x 3" D enclosure.
If that was all two wire circuits that is 180 conductors, IMO it would be tough to keep neat.
If it is a case where 200 amps is enough power and you can locate the panels side by side get one panel Main breaker feed through style and get a second 200 amp main lug only panel.
Nipple them together with a couple of 2" nipples and for all intents and purposes you have 84 circuits in 'one' panel.
Construction & Maintenance Electrician