I think cameras in the MLG wells may be the best option. Some airports will always have crap security, and allow these people to stow away.
Why oh why in todays security climate people with ramp access are not screened like pax is beyond me. Even cargo from the "trusted shipper" scheme is not reguarly x-rayed and checked for explosives and the like.
I'm no security expert, but it seems to me like the weak link in the chain.