Note that the Great Crowd are also in the naos (temple santuary) rendering sacred service day and night. They are not in the heron (the temple grounds). Revelation 11 shows that the courtyard is not the same as the naos. Therefore, if they render Sacred service IN the temple, that implies a priestly duty. Thus, it blows the Society's arguement out the water.
Revelation 7 is outlining two groups that survive the Great Tribulation which ended in 70. The 144000 are the faithful remnant of Israel who take thier Exodus from Babylon (first century Jerusalem) and thus are saved from the destruction upon her. Just as a vast mixed company joined the Israelites in the Egyptian Exodus, Revelation points to a Great Crowd of those who are saved through the Tribulation that are not fleshly Israelites.