Understand the contractual meanings of 'shall', 'will' and 'should'! It's hardly rocket science to develop such an ac given Airboos' background in CAD/CAM and aerodynamics - what is critically important is end-user input at a formative programme stage. Because once the spec has been firmed up, no amount of 'but what we wanted was...' whinges will cut the mustard with the bean counters!
I remember how it took many years and cost much money to install 2 never-needed lights and switches on the VC10K (and eventually to all VC10s) - because no-one asked the aircrew first! (HF Auto/Man tuning switches if you really want to know. They were installed 'Auto' - but everyone wanted 'Manual'. Hence 'they' spent lots of dosh on 2 little green lights and 2 switches to select HF1 and/or HF2 tuning to 'Auto' or 'Manual'. Can't remember when anyone last selected 'Auto'!)