As a halfway answer to this, I ask if specific plane types are required on these routes. If not then swap out current craft for smaller vehicles so that your pilots can maintain proficiency time while still moving cargo and the reduced number of passengers. Flying isn’t like riding a bike and pilots can’t sit in simulators ground-side indefinitely. You won’t be swapping in a Dash 8 for an A380 in every case but smaller Embraer jets in lieu of the Airbus heavies could help keep the training/proficiency side going.