Record parsing to Scala object with some unknown fields
I would parse the row into a Map[String,String] first (by collecting the key-value pairs that you already know how to split), and then do

this.imptField1 = map.get("imptField1").getOrElse("")
this.imptField2 = map.get("imptField2").getOrElse("")
this.remData = map  // just the whole Map, or maybe remove the above two keys


I would also change the class to be immutable and move the parsing code into the companion object (it would do the parsing, then pass the map to the constructor of the class which can directly assign to its val fields).