Ability to have optional Signature Fields in PDF without having the declarative

Currently in our PDFs for Lending purposes we often have predefined signature fields on the form for up to 4 parties, although in a typical application , we may not always have 4 parties. As such , when I submit a JSON with the number of Signers less than the actual number of signature fields on the PDF, there is an error.validation.extractingFields, stating it couldnt extract the Signer2 where the latter is the name of the textfield in the PDF.