I remember many, many years ago that British Airways at Heathrow required their hangar personnel to wear helmets after rash of head-related injuries, so this is not a new concept. However, if the engineers/technicians of your former company are concerned about their abilitiy to carry out inspections thoroughly while wearing helmets (I'm assuming here that we're talking about conventional hard-hats as used in the offshote industry etc.) then why not try the type of helmet that do not have brims and peaks, the type that rock-climbers favour. these will allow the wearer to maintain his/her peripheral vision while still having head protection.