Wow this is a revelation! Please can you point us how the volume for external views can be adjusted without touching what you hear inside the cockpit with "hear like in helmet" checked?
I'm struggling to find the solution but it seems it was under our nose all the time :)
Looking forward for a reply.
Sorry but you are not correct here. Sound is a physical phenomenon, and the world is plenty of tools, measurers and math models to describe it correctly.
Just to state it better: SOUND IS NOT SUBJECTIVE, sound is something you can measure, model and reproduce accurately.