Arresting based on what? There are unfortunately no hard evidences against upper management at the moment.

They should treat it as they would any other conspiracy. You focus on an individual, arrest them, then get them to give evidence. Eventually you work your way up the chain. Waiting until you've got all the ducks in a row is special treatment in comparison to standard criminal investigations.

Up to 14 months are paid.

You've forgot to mention that up to 14 months from those 3 years are paid.