I probably wrote this piece over a decade ago. At that time, the Witnesses' understanding of the "faithful and discreet slave" was that the designation applied to the anointed on earth at any given time, beginning with Pentecost 33 CE.
True, Matt. 24:45 does not necessarily teach that the "slave" is more than one person. But since the text is embedded in the Olivet eschatological discourse, and since the "slave" is appointed before the Master leaves and is still present when the Master returns, it is quite likely that the "slave" does consist of more than one person who feeds a household of slaves. Francis Wright Beare writes:
"Slave--the figure reflects the fact of slavery in the ancient world . . . The parable, then, pictures the church as a great household with a staff of slaves, and concerns itself only with the head slave."
"Since the monarchical episcopate had not yet developed, it cannot be supposed that the parable presupposes that the church is ruled by a single head. If it does, we should have to think of it as applying to Peter, or(conceivably) James, who soon became head of the Jerusalem church. But it is better to see him [the slave] as a figure of every one who is in a position of responsibility in the church" (Francis Wright Beare, The Gospel According to Matthew, page 477).
While I do not think that the "slave" is restricted to those who have responsibility in the "church," I think Beare's comments show that the "slave" could be more than one person.