It will be a costly, but probably far more effective and cheaper, in the long run to have more permissive sick leave allowances and more open reporting of mental health issues with an accepting culture.
......hmmm..
I'd think it would be more appropriate having shown during initial training that you have mental illness you should not be eligible for a carrier as a professional pilot. If it were only somebody being depressed for week, maybe even a fortnight fine. Anybody can end up there but here we're talking several months!!
Lufthansa has some explaining to do, it would seem.