Seems one solution could be for officers to use loudspeaker to state why they are outside, and give very specific protocols for safely exiting the residence. Possibly offer a communication channel to dispute validity of their arrival. I imagine they have the phone number of the land-line or cells within a certain radius of the residence, along with social media profiles they could examine to 'profile' participants in the situation and assess validity. You can't have a system that solves the problem 100% and is immune to being gamed by criminals, but with data and clear lines for communication it seems you could pretty easily create a reliable 'safety net' for people caught up in fraudulent 911 calls without exposing the responding officers to any risk.