After searching the Object Model Viewer (OMV) of the ESTK and Jongware's corresponding html-documentation, I fear that it is not possible to script InDesign's Ink Manager. Please, correct me if I'm wrong…
I'm not sure, but try to check ConvertToProcess property in all Inks
Property ConvertToProcess As Boolean
Member of InDesign.Ink
Converts spot inks to process inks.