This is an exerpt from the book Maximum Impact Short-Term Mission by Roger Peterson, Gordon Aeschliman, and R. Wayne Sneed.  Arguing from Matthew 5, they make the point that any missions work that seeks to conform to God's plan for missions should (must) involve average believers:

Important to note is the orginal Greek tense Matthew used in verses 13 and 14 (present indicative).  In other words, average, real, foolish people are already the salt and light of the earthly Kingdom of God- whether or not we want to be is of no accord. Further, the verb tense used is not a verb of action, but a verb of being, this only serves to emphatically emphasize the believer is already the salt and light of the world- regardless whether the believer understands it or not or likes it or not.

   

But perhaps the greatest significance derived from Matthew's original text lies in the structure both sentences use to start verses 13 and 14.  Jesus' statements about already being "the salt of the earth" and already being "the light of the world" both begin with the use of the personal pronoun ("Ye are...").  Lutheran pastor and theologian Todd Wallace observes "this is not technically necessary because the person is implied within the verb form.  When a personal pronoun is used to begin a statement of being it is always for the purpose of intensifying the point being made.  Literally, in English we would render it as "You, yes You! are (already) the salt of the earth...."

     

MISSIO ECCLESIASTO must conform to MISSIO DEI.  Any man-made plan of mission which sidesteps real, average believers who are already appointed as God's salt and light, overtly circumvents the design of God.  Therefore it behooves us to ask the obvious question: are we structuring our Great Commission efforts to purposely include the foolish, the weak, the low, and the despised (i.e., the real people) in our churches?  If not- then according to God's Word- we are refusing to conduct MISSIO DEI God's way.  (page 18)