I suggest to add arguments like this:
/validateSubstitions Validate substitutions, return an error if any
substitution settings are undefined.
/validateXml (/v) Validate XML, return an error if the result
document is not well-formed.
/validate (/v) Validate settings. Turns on the following validations:
This would also enable to only test for well-formedness, if someone would wish that. Furthermore it opens up for future validations.
An alternative is to let noDirectives imply not to test for well-formedness. This can not be recommended however, because using noDirectives with xml-files are perfectly fine.