Tertullian

Tertullian (c 160 - c 225 AD) was a prolific Christian writer from Carthage, North Africa.  He was the first to use the term Trinity and explain that doctrine.  He never refers to himself with any title, so he may have simply been an educated layman in the church.

Tertullian was never made a saint in the Catholic Church because he held some controversial views.  However, he wrote against many heresies and covered a wide range of theological doctrines and church life, which help paint a picture of the church in his day.

In regards to church leadership, Tertullian mentions one bishop who has authority over the elders and deacons, similar to what Ignatius taught.  However, where Ignatius required the bishop to be present for baptism, Tertullian states that any believer can baptize with the bishop's permission.

"Of giving it [baptism], the chief priest (who is the bishop) has the right: in the next place, the presbyters and deacons, yet not without the bishop’s authority, on account of the honour of the Church, which being preserved, peace is preserved. Beside these, even laymen have the right; for what is equally received can be equally given."  (Tertullian, On Baptism, chapter XVII)

Tertullian argued that baptism should be permitted for children, but only when they were old enough to know Christ and to request it.

"The Lord does indeed say, 'Forbid them not to come unto me.'  Let them come then, while they are growing up; let them come while they are learning, while they are learning wither to come; let them become Christians when they have become able to know Christ."  
"Let them know how to ask for salvation, that you may seem at least to have given 'to him that asketh.' "  (Tertullian, On Baptism, chapter XVIII)

Broadbent suggests Tertullian is arguing against the baptism of infants, but Tertullian does not mention that per se.  He clearly is arguing for believer's baptism though.  Broadbent also mentions that Tertullian condemned the practice of baptizing the dead, but I could find no reference to that practice in Tertullian's writings on baptism.

Broadbent also quotes Tertullian regarding the freedom of religion.

"It is no part of religion to compel religion, which should be adopted freely, not by force."  (Broadbent, The Pilgrim Church, p. 33 from Tertullian, Apologetic To Scapula, chapter II.)

This freedom would be severely jeopardized in later years as the Catholic Church sought to compel orthodoxy through brute force.