Squawk standby ...
I'm not sure my answer would completely answer your questions and clear all the dilemas you have about the subject ...
Visual departures are defined to some extent ... check out Regional Suplementary Procedures Doc.7030 (6.5.4. Visual departures) for EU Region ... so this one could be used if pilots want some immediate turns after departure where they are legally responsible for the terrain separation ..
In-flight situation: any deviation from SIDs would not be approved by me until above MRVA(MSA) due radar minima ... but i guess PIC (whos responsible for her\his plane and the passengers would take any action necessary in their view to conduct a safe operation. Thats their responsibility.
1999