SASless:
If they are "Crew"....then CRM, duties and responsibilities along with liability follows that inclusion
I currently fly with "crew". They are cabin crew. They have duties and responsibilities too. They do courses in CRM. Some of them are also qualified pilots.
The fact that they are "crew" could not ever make them even remotely liable for any accident in which the pilot(s) may be at fault. Because the driver(s) are specifically and extensively trained to bear that exclusive responsibility. The word 'crew' simply means the individual has a role to play on board. In no way does it imply any responsibility for that 'flying sh1t'!
The fact that 'the reality' may be subtly different is frankly neither here nor there I'm afraid. You correctly mention the ANO and FAA rules say 'one thing'. You needn't look any further.
That is precisely to prevent the blurring of lines (which some around here seem to wish) that could result in totally innocent people being burdened with utterly undeserved opprobrium.
As I said in my PM to you last night, that would be cowardly.
I'm just sticking up for the observers here. Any suggestion of their 'liability' is from the Walter Mitty world in which the likes of 'chopjock' live I'm afraid.