Unity without diversity would produce uniformity, and uniformity tends to produce death. Life is a balance between unity and diversity. As a human body weakens, its "systems" slow down and everything tends to become uniform. The ultimate, of course, is that the body itself turns to dust.
This helps to explain why some churches (and other Christian ministries) have weakened and died: there was not sufficient diversity to keep unity from becoming uniformity. Dr. Vance Havner has expressed it, "First there is a man, then a movement then a machine, and then a monument." Many ministries that began as a protest against "dead orthodoxy" became dead themselves; because in their desire to remain pure and doctrinal sound, they stiffed creativity and new ideas.
Each ministry is designed to edify the body of Christ.