As I posted on the other thread that chimes in with what I was told by a pilot who'd flown both in action in WW2. I don't think there was any formal consultation system
However in the war pilots were not afraid to voice their opinions - most of them were young, they weren't career pilots and they were likely to die if someone gave them shoddy kit - so opinions were voiced and listened to
The Manchester was a case in point - the pilots loathed it's engines - there were several others that also only had very limited frontline service due to feedback from the front.