So, option `class D(A)` with the `.safe_copy()` is the only safe thing to do. That doesn't change crontabber/app.py's `CronTabber` class. 

What I have here is basically the same as `class B(A)`. 

Which do you prefer? B or D? 

One thing is for sure, introducing a new class (`CronTabberWrapper`) is pointless and needs to change to be like `B` or `D` based on your preference.