Limited view point
On the exec side, the JAR has made life much easier. I obtained my JAR licence on the first day of CAA compliance, and was working in Denmark, the JAR was held by serveral of the guys, from many different countries. My next Job, Zurich operation, the JAR is the norm, with several nations represented.
YES some countries prefer their nationals, but several prefer expats, (many benefits for the company, in relation to local social costs).
As to is it needed, many of us have no JAR licences and continue to be paid each month, but in the long term GO FOR IT.