If the latter option is chosen, police protection is needed 24 hours a day, seven days a week, which creates a Sabbath-work dilemma. If the entire nation is Adventist but surrounding nations aren't, we have an even greater problem of protection from aggressors. The church life and personal life of NYC Adventists presuppose the availability of electricity on Sabbath. Church sanctuaries are so large that a speaker would never be heard were there no sound system. Lighting, air conditioning and heating are taken for granted.
Food has to be kept cool.
Even on Sabbath, Adventists depend on subways, traffic signals, elevators, and life-support apparatus at hospitals. All of this is made possible by electricity. And this electricity comes from a power plant somewhere, which is operated by human beings. There would be similar concerns with water supply, sewage disposal, fire protection, and snow removal. If the entire population of New York City were Seventh-day Adventist, church members would have to run the hospitality industry, if it continued to exist.