"I don't think we are seriously suggesting - at this stage in our development, that 24 hour EMS ops are really viable."
Not only possible, but long history of success. It is the most hazardous phase of EMS, but seems equally risky in all types of equipment single/twin and vfr/ifr.
Yes, I have been IIMC at night on the job. Fortunately, our fleet's better equipped than what I flew for Uncle Sam in Vietnam, so staying on the gauges long enough to get back to VMC has been an exciting inconvenience, at most. Almost all my IIMC encounters have been on takeoff and would not have occurred with any type of assisted night vision- and that opinion's based on my experience with "Starlight" equipment, 40 years ago. There's no comparison with present technology.
The most damning failure in US EMS is the fact that NVGs are only now being fielded in any real numbers. Keep your radar altimeters, TAWS, xenon spotlights, dual GPS, glass cockpits- I want to SEE what I'm taking off and landing into, and NVGs do that better than anything else. The military's NVG use has proven it, decades ago.