Surely if static is an issue it is worth earthing the disconnected battery earth cable to a real earth point outside the car?
If one is really concerned the technician should also be earthed, as is normal in the electronics sector. Usually and ankle earth band and wire is enough, but it might be a problem for someone moving about a car.
Final thought: how long are airbags effective, in that do they have a shelf life? So, after for example, 15 years, should they be replaced?
