Is it planned to have secondary and additional parameters? Just to take simple DCV function for example:
Tempco factor (with ACAL and without ACAL ;)
High-voltage additional uncertainty due to HV divider heating
Factory calibraiton adder
Noise specification adder from fast modes of operation
Null errors for lowest ranges (esp important for nanovoltmeters and small signals)
Often resistance also have various modes with different specs (e.g. OCOMP ON or OFF).
It's impossible to have useful calculation of instrument provided uncertainty without having complete specs dataset.