How to Batch Change Project Units

Revit
2

Have a look at my code here to see if that helps - Change project unit node - #2 by Mike.Buttery

weight = SpecTypeId.Weight
kg_force = UnitTypeId.KilogramsForce
current = units.GetFormatOptions(weight).GetUnitTypeId()

if current != kg_force:
    units.SetFormatOptions(weight, FormatOptions(kg_force))

# etc.