The navigateTo method is lacking in the ability to pass an optional data dictionary object. Some of the other pageInput types do include this. But the Custom Pages type does not.
Currently I have a need for this as I am triggering of a onChange event for a field in a non saved record , in my JS I set up the navigate options and utlizing the recordID field I am passing the field name. (not the intent of the field). I would also like to be able to pass along the other fields/current state of the records data etc.