The actual answer is the fact that there is a Biblical Christian "temple" sect that is supposed to appear after "2300 evenings and monrings" that is 1150 years into the final 1260 years of the covenant that end in 1996. That means this special "temple" sect would appear in 1886 and function until 1196. That is:
36 CE ends the 70th week of 70 weeks, beginning 455 BCE and ending 36 CE. This establishes the sequence of covenant weeks.
70 weeks = 490 years
4 x 490 = 1960
1960 + 36 CE = 1996 AD
Thus in 1996 AD the covenant Period ends for both Jews and Christians. That specifically includes the "temple" sect that appears in 1886.
If you maintain the concept that a "slave" is in charge of a sect or cult or ministry, then we learn from the parable of the ten slaves sent out with silver money to do business, that Christ gathers in many places. In fact, he says specifically after removing his "little flock" that he has "other sheep not of this fold." So even though that temple sect, like the tribe of Levi, was chosen to perform special, high-level spiritual tasks, it is not the only "chosen' group. It is only one of many others.
However, looking at other scriptures we find this "temple" organization would have an ego problem among its leaders. They would rise up in God's temple of public anointed ones and make itself a god. This is the "man of lawlessness" mentioned at 2 Thess 2:3,4. So the irony is, whichever organization is the true temple in its right condition after 2300 evenings and mornings is the same sect that becomes the evil slave organization and produces the man of lawlessness.
So that's the dilemma of the WTS. It knows it is the chosen temple sect, the sect that would preach the "good news" and the sect that would be the target of Gog of Magog (German Nazis) alongside God's other "holy ones", the natural Jews. Case in point, when Matthew speaks of the "love of the greater number cooling off", it is speaking of the natural Jews and the growth of antisemitism leading up to the Holocaust, which was the first "great tribulation" (of Matthew, not Revelation. One tribulation occurs before and the other after the second coming). Of note, Jews and JWs were targets of the "disgusting thing that causes desolation" which is Nazism. If the Jews are the "greater number" then the "lesser number" is a reference to the Christian holy ones. There was a reason JWs were targets of the Nazis along with the Jews. They fulfill how the disgusting thing stands in the holy place, that is, attacks the holy ones, who are Jews and JWs.
Here's a video you might find helpful that elaborates on this:
http://www.youtube.com/watch?v=CnTy8_EhE0Y
They also specifically full that the good news would be preached world wide first, and then the "end" will come. The end is not Armageddon. The end is the end of the gentile times which ended on November 30, 1947. That very year, then president N.H. Knorr did go on a literal around-the-globe speaking tour, thus fulfilling that when the good news was preached world wide, the end would then come. And it did.
So there is no getting around JWs being the "temple" sect, but only one slave out of many who gather in God's approved elect. Even so, this temple of anointed ones would become corrupted apostasy and when Christ comes he has to separate out the sheep from the goats. These sheep separated out represent the "wise virgins" and the "little flock." To them he says, "I have other sheep, not of this fold." This slave organization, JWs, are thus many times referenced as the "evil slave" and the "sluggish slave" or the "man of lawlessness" or the "false prophet." All these refer to the WTS after they became apostate.
The GB was "disfellowshipped" by Jehovah on November 20, 1992. They are now in spiritual darkness and headed to the lake of fire like the rest of Christendom.
Of note, in 1886, the first Studies in the Scriptures appeared. This volume series became the doctrinal foundation of the Bible Students who later became known as JWs.
So Who really is the FDS? It is Jesus Christ. JC appears 45 days after the GB is disfellowshipped, that is, identified. This fulfills 2 Thess 2:3 "Let no one seduce you in any manner, because it will not come unless the apostasy comes first and the man of lawlessness gets revealed, the son of destruction."
So the second coming does not come until after the man of lawlessness is revealed. He was revealed on November 10, 1992. 45 days later on December 25, 1992 is when the second coming took place. They were revealed by a direct leter to them that they were being cast out and that they fulfilled being the evil slave. This letter was sent by one of the anointed who called himself "The Watchman." Likely F. Franz and the WTS figured this person would become the messiah so assisted the UN in trying to prevent the 2nd coming on December 21, 1992 as preached by the "two witnesses", two of the 10 slaves who witness for Christ. They were successful, but the next day Jehovah killed Fred Franz on December 22, 1992. At this time the WTS had just joined the UN in early 1992. With Franz' death and Jehovah's help the 2nd coming took place uninterrupted on December 25, 1992. This fulfilled the 1290 days and the 1335 days in relation to the 70th week that starts in 1989 and ends in 1996. Per Bible prophecy, the messiah must arrive sometime after November 30, 1992 but before April 6 (Passover), 1993. So all was fulfilled on time. Turns out, it indeed was the messiah who wrote the letter to disfellowship the GB and reveal them as the "man of lawlessness."
But in answer to your question, Who really is the FDS? The answer is, of course, the returned Jesus Christ himself. He is the one whom Jehovah places over all his domestics while the GB of the WTS is cast outside. They are not the FDS, they are that "evil slave" who beats up on his fellow members because they think the master is delaying in his return. Which fulfills the state of the WTS right now. They are waiting for the 2nd coming to happen and keep extending that "last generation" concept. So they are frustrated. But they have the wrong chronology. The correct chronology dates the fall of Jerusalem to 529 BCE and thus the 2nd coming in 1992 rather than 1914.
So the true faithful and discreet slave turns out to be none other than Jesus Christ, returned in the flesh. The "evil slave" turns out to be the WTS, who served as the "temple in its right condition" (Daniel 8:14). The covenant with Jews and JWs ended in the Fall of 1996. Now the Covenant is with spiritual Israel who are now all but sealed into the kingdom, some 1,440,000. The 144K are only the natural Jews (Isa 6:13).
You're most welcome!