If the 'request' really gives one serious anxiety (and I'm not talking about being flexible or JUST extending one's roster to ease a problem), one well-practised tactic is to ask the manager concerned to 'pop that on a telex/fax', and this often causes a 'review' in the mind of the manager. I heard of one-such who 'ordered' a Captain into discretion - and sent the requested telex. I think there was a bit of a fuss.
I was once 'asked' to do something quite illegal in a big airline and asked for it 'in writing' to be told 'I couldn't possibly do that' - to which I replied............................
This goes a long way to solving your penultimate paragraph.