Too much logic. You also make it sound like a challenge to the unions. Never, ever underestimate the stupidity.Was thinking the same thing. Get a list of all people with evidence of corruption against them or any other formal misgiving. Get an independent labor law specialist to review all the cases and put them into 3 different piles. Those who can be immediately dismissed due to severe transgressions, those who can possibly be dismissed after formal grievance process is followed, and those who require more evidence or investigations in order to start dismissal proceedings.
If they dismiss people in accordance with the labor laws, the unions can't get upset and strike because they would then be showing they support illegal activities, and the people who are dismissed are likely spread evenly over the organization, so you aren't putting a single division at risk by getting rid of them.
The best thing about this is you are getting rid of the bad apples and leaving the good ones. If you offer retrenchment packages, it is likely the good ones will take them to get away from the rotten apples, leaving you with nothing but a basket of rot.