I can see both sides of the argument...
Orthodox Jews who have religious objections to such national service, and many countries, including the United States, make provision for Conscientious Objection based upon religious grounds...
...and...
Those serivice-shy Orthodox Jews live under the shield of the national government and are being protected by the efforts and sacrifices of their fellow citizens and need to begin making more of a manpower contribution to both national defense and national service...
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For my money - if I were king of the world - I would consider requiring them (those Orthodox Jews who refuse to serve in the IDF) to choose between (1) service in the IDF alongside everyone else, or (2) some other form of national service, for the same time-period required of those serving in the military.
As an incentive to choose the military, I would even consider conjuring-up three sets of National Benefits packages - one for those who served in the military (the best package of all), one for those who served in a lesser national-service capacity (a lesser package), and one for those who refused to serve at all (the least generous package)...
But that, too, opens-up a can of worms here and there.
Bottom line, this is an Israeli internal matter, and one that they must decide for themselves.