I find the revolving door between government and private industry troubling but I'm not sure it would be a good idea to employ such a ban.
This is obviously very anecdotal but I have two prior service friends, one an infantry Marine, the other a Navy Cryptologic Technician, and they are the two most anti war, anti mass surveillance people I know. Far more so than most of my other friends who don't have any military experience, and my social circle tends to lean heavily liberal.
Isn't that... a political solution?
Obviously there are dangers of going towards oppression. But at the same time Europeans are saved by internal division between member states. Most countries are so small that they cannot pay or accomplish spy programs like the Americans can. And collaboration between countries hardly happens, as we saw in terror attacks.
Things only become problematic if European intelligence agencies come into existence.
Technical solutions are the only possible answer, that and cultural responses.
Vast state surveillance is made possible by technical expertise. We shouldnt laud those who assist the government in this task nor in any tasks. We should shun colleagues who choose to assist the enemies of humanity, those in positions to hire should not hire those with backgrounds in government and make it known through back channels that such people are not desirable, that you will be black balled if choose to assist these heinous entities in their oppression.
Finally those able and willing should consider other methods of raising the cost of state surveillance, but openly recommending such things is potentially a crime in the eyes of the state.