Many years ago, we scoped out what it would take to do this. Here was the list of items we produced at the time; I can't say whether it covers everything, but it ought to be a good start.

• Update winter/summer design days for all internal schedules based on Manual J approach (Internal gains should be 0 for winter design load calculation)
• Include winter/summer thermostat schedules based on setpoints used by Manual J approach (75°F for cooling, 68°F for heating)
• Update Sizing:Zone and Sizing:System 'Central Cooling Design Supply Air Temperature'
• Update Sizing:Zone and Sizing:System 'Central Heating Design Supply Air Temperature'
• Update Sizing:System 'Design Outdoor Air Flow Rate' to 0 m3/s
• Update Sizing:System '100% Outdoor Air in Cooling (and Heating)' to 'No'