Lonewolf,
Thanks for coming back and making a very good point about form fit helmets that I'd completely forgotten about. Yes, those inners will be unique to a person, and not in a pool.
I think that as things like HMDS become more widely used (and they will) then the lessons learned with NVGs will have to be applied. A few years ago, it quickly became apparent that getting NVGs properly serviced, fixed and set up was well beyond what the SE trade had been trained to do. So, we had to stop treating NVGs as bit of 'flight equipment' and start treating them as avionics kit. So that's what we did.
The avionics 'guts' of future helmets are a very big step along the same path, in my view, every bit as complex and dependent on maintenance as the black boxes and software fitted in the aircraft.
However, I'm hopeful. People at the front line (and those devising support systems) are intelligent, adaptable and ingenious. Honestly, sorting out how to maintain and service these items isn't rocket science.
Best Regards as ever to those in the workshops
Engines