Regarding the distinction between the "little flock" and the "great multitude" among the original Bible Students: The one hope of their calling was to become members of the "little flock" - to reign as kings and priests with Christ - and only as a consequence of partial unfaithfulness would someone end up in the great multitude. The great multitude was expected to be a secondary heavenly class similar to angels, but one did not enter the race for life with the expectation of belonging to this secondary class. It would only be in the resurrection that one would know for sure what the final outcome was. In the meantime, all were anointed, all were spirit-begotten and partook of the Memorial emblems. So it was not like today (when the "great multitude" is considered earthly) that each one was expected to identify as belonging to one group or the other.
As for the original context in Luke in which this expression "little flock" occurs, it certainly is a prime example of taking scriptural terms and phrases out of context and repeating them over and over again. But nevertheless, it is beneficial to ask whether or not it is a term which is applicable only to the original evangelical milieu (belonging to the context of Jesus' earthly ministry and peculiar to the gospel stories) or if it could, by extension, be applied to the church after the change of dispensations. The reason I ask this is that none of the New Testament writings were directed to Christians living in later times, and yet they are commonly applied to such. For example, Paul told the Corinthians that they were the "body of Christ," and yet all Christians understand that they belong to this "body" (JW "other sheep" excepted). Of course, once the number of Christians increased, "little flock" would not seem to be an appropriate description, but I wonder if any other Christian groups have applied the expression to themselves.