The original Directory for Publick Worship makes no provision for anyone to read or preach other than a minister.
Where exactly does the directory "OK" reading another's sermon?
"It is presupposed, (according to the rules for ordination,) that the minister of Christ is in some good measure
gifted for so weighty a service, by
his skill in the original languages, and in such arts and sciences as are handmaids unto divinity; by
his knowledge in the whole body of theology, but most of all in the holy scriptures, having
his senses and heart exercised in them above the common sort of believers; and by the illumination of God’s Spirit, and other gifts of edification, which (together with reading and studying of the word)
he ought still to seek by prayer, and an humble heart, resolving to admit and receive any truth not yet attained, whenever God shall make it known unto him. All which
he is to make use of, and improve, in
his private preparations, before
he deliver in public
what he hath provided." (DPW, section on
preaching the word.)