I think that the four titles (hearkening to Zechariah's Four Craftsmen) each concern Jesus Christ directly. Reading His words about Himself in 3 Nephi, these four roles (not genealogies) are wonderfully covered. "Messiah ben Joseph" in particular as the Messiah for the children of Joseph as described in Chapter 21, where He brings forth the sign, which I take to be the fulness of the Gospel, as the prophet of whom Moses spake. Joseph Smith and every other servant are those spoken of in 3 Nephi 20: 40, and support these four roles. The servant (of the Father) is still Jesus Christ, and He does His own work.
Chapter 21 is written in a way that Christ is referring to Himself, not Joseph Smith. For example: "I shall gather in... I will give unto you for a sign... repent and come unto me and be baptized in my name and know of the true points of my doctrine, that they may be numbered among my people... " He gives the man (Joseph Smith) power to bring these things and Jesus words forth (verses 9 - 11), but this renders Joseph Smith a type for this aspect and not the Messiah ben Joseph, though the prophecies of Joseph of old, including genealogy and name, point to Joseph Smith in that sense.
I suppose given modern revelation we could tie each of the four roles (Messiah ben David, Messiah ben Joseph, Elijah, and the Righteous Priest) to the plan of salvation with the atonement of Christ at the center, the sign of the fulness of the gospel coming forth, the sealing power, and the Millennial Reign, respectively. John the Baptist served under Messiah ben David, Joseph Smith under Messiah ben Joseph and Elijah (but perhaps a future prophet will restore and exercise more aspects of the sealing keys -- see Helaman 10), and others (the 144,000?) under the Righteous Priest.