I see Science Fiction and Fantasy similar to Myrthman, a fictional parables to illustrate or introduce Christian values and worldviews to people who wouldn't necessarily be exposed to them otherwise.
(That could include church kids by the way. Many pastors kids that I know testify that they "never heard" much of the gospel message and bible truths growing up. That is none of it sunk in because they didn't have genuine faith until later in life.)
I started writing Space Operas and Fantasy/Mystical reality stories to try to reach the intense secularists and evolutionist fanatics over at Baen's Bar. They have a ground rule that no one can question the fact of materialistic evolution. I figured that if I wrote space opera I could slide Christian worldview in under the radar. Hey, it worked for Dave Webber and a few of their other superstar writers.
I managed to get a some positive responses to some of my early efforts at writing (a miracle in itself, <shudder> my early stuff was poor, stylistically) where I peopled Space Operas with realistic Christian characters and showed how they reacted to stress and the unknown.
The biggest response I got was one other Barfly who said that he wished there was an overarching "God" who controlled things providentially and gave hope beyond this life.
I feel that my writing in the Sace Opera, Mystic Reality (like Magic Reality except overtly Christian), Alternative History and Near Future genres is a way of redeeming my earlier Science Fiction fanaticism. I used to devour the stuff by the boxfull. I read all the greats of the 1950's - early 1970's.
Now if I can just learn the craft well enough to get published.
I feel that our general calling in the Sf writing field it to relay the foundations of Christian worldview and personal principles in a Neo-Pagan world. I feel that we write so God can use our work to counter the perverted view of Christianity that the Satan dominated popular culture and mass media is pushing on people who don't know any real Christians.
Beyond that I guess my views of the fantasy elements are like the pioneer missionary's views of integrating him/herself into the pagan cultural milleau to find the concurrances with the Gospel so he/she can reach the unsaved. "I'm made all things to all men . . . if by any means I may save some."
It seems that in every church age the "high Church" conservatives have always criticized and in some cases Anathemized the most radical mission and evangelical minded branches of the church for thier "Non-Conservative" approach to church and life. For instance the early Salvation Army was roundly condemned by the 3rd and th generation Methodists for using barroom and Circus songs in their worship (ie. Oh Happy Day, I've Been Redeemed to name two).
The churchy crowd (read christian Pharisees) felt the the music was polluted by it's sinful association and the fact that the words were powerful salvation testimonies was a blasphemous perversion of the gospel message. They reasoned that the "Gospel" needed to be "Protected" from any contact with sin or sinful ways.
Um, . . . excuse me; Light erases darkness, Fire eliminates cold and purifies pollution, God's Life in Jesus Raises the dead; and The Gospel in the Power of the Spirit destroys Sin in peoples lives and raises them up from their dead works to new life in Jesus. We are supposed to take the flaming Gospel Torch of life into the middle of the camp of dead sinners and bring them to light, not hide the truth behind closed doors in our cloistered churches.
;D Ahem, sorry. I was a rescue mission pastor in my days of strength and health. "To preach the Gospel where Christ was not named" was the life verse God gave me.
If you're writing for the Christian Booksellers Association market then you are constrained by their "rules". I think they are too narrow and that's why we're in danger of losing a generation when our young people find out that real life doesn't work like those marshmallow creme Sunday School paper style stories. ( a bit of hyperbole there I suppose

) That's one of my pet peeves. But if you're writing for the CBA you're probably not writing Sf anyway because they don't like that genre.
However if you're writing for the lost world, or the lost kids within the church world then Sf may be a very productive genre for Asymmetric Evangelism. Just look at the explosion of interest in pretty hard core Science Fiction and Fantasy in the entertainment world. Contrary to the Churchy tut-tuts The Star Wars series in the Late 1970s sparked the crumbling liberal demociacies of the West to a new stand against Godless communism; and it also was used of God to bring many people to true faith in Jesus (with the help of those who used the spiritual types to show them the Gospel and the real Jesus).
Jesus was criticized for hanging with the wrong crowd, in the haunts of sin, and for ministering to people in un-orthodox, unapproved and in many cases "Illegal" ways (according to the orthodox cannon of proper religious practices). If he was called a "Demon Possessed Heretic (Samaritan)" then we can expect that anyone who dares to follow his example will be called the same or similar.
Careless seems the great avenger
History's pages but record
One death struggle in the darkness
Betwix't Error and the Word
Truth forever on the Scaffold
Error ever on the Throne
But the Scaffold sways the future
and beyond the great unknown
Standeth God within he shadows
Keeping watch upon His own.
Whitman
If you want to know the true character and power of a church or religious movement, don't look at the grandeur of their Bishops, Priest and preachers; Don't delve into their great theological works or the great theological scholars they've given to the world. Instead look at ranks of their Martyrs. Find the track or their bleeding footed sufferers, carrying the sufferings of Christ for their generation. There, only there, is the power and greatness of the Gospel of Jeus found in that church.
In Heb 13 Paul commands us to go forth from the established temple crowd, go outside the gate of the city to the garbage dump where Jesus died on the cross for us. He went outside the gate to bear our sins, we need to join him and "bear His reporach" out there to reach our generation for God.
When the Scribes and Pharases criticized Jesus and his disciples he told the disciples, "Ignore them, every tree my Father hasn't planted will be rooted up."
Many things, attitudes, prejudices and dogma's in the church world are "human cultural artifacts" that people have dragged in with the from the world. They are not "trees that the Lord has planted". They are not truly part of the simplicity of the Gospel that God gave us to take out to the world.
If God has called and sent you into an Unorthodox avenue of Gospel proclaimation (as He did me) then make sure it's him and not just your own preferences, then "keep youself in the Love of God (Not Religion but Faith that Expresses itself though [Christlike] Love [Gal 5]) by praying in the Holy Ghost [Jude]" and have at it with all your strength, energy and wisdom.
Jesus gave us one job to do while we wait for his return in victory. It's called the Great Commission. The church world (or is that the worldly minded church) has been piling all kinds of other things onto the to do list for Christians ever since Jesus ascended. IMHO most of them are inspired by the Devil (wisdom from beneath [James]) to slow down the fulfillment of preaching the gospel to every creature. I'm convinced that is why the "Christian west" has lost the last few generations from Christ. Luther said that the Simple Gospel is the only antidote for he worldly mindedness that is programed into our nature. The other Churchy stuff distracts us and d**n's our kids.
My current church fellowship is part one of the largest and most aggressive missionary minded associations of churches in the world today. We have been turning away from the traditional, "Orthodox" models of missionary activity and evangelism to more organic, and in some ways ancient Celtic, methods of reaching the pagans around us, because the "orthodox" methods were not reaching the lost that we rub shoulders with every day. People stopped getting saved in our assemblies so we are resetting the models to find God's ways of effectiveness in our great commission work. In our estimation NOTHING is more important. (that by the way is why I'm a member of this fellowship today, that's how I think a true church should behave)
I suffered a physical breakdown in 2008 that left me too weak to continue preaching on a regular basis. God spoke to me and told me that I was to start writing as an outlet for my prophetic (inspired preaching) ministry since my physical was too worn out to support the preaching ministry any more. He led me into this as an outlet for the inspiration He continues to pour into me. I'm as sure of that as of my Salvation.
40 of my 62 years have been spent trying to get the Gospel that saved me to others who haven't yet heard the life changing news that Jesus died to save us and make us his own. During most of my public preaching ministry somebody has always been criticizing me and condemning what I was doing because it didn't fit their idea of "Holiness" or "Decency and Order". All I know is that God opened the doors to get the gospel to unreached groups of people and I walked through in faith.
When I did that He always answered by Holy Fire. The Critics usually condemned that too, they don't like the way God does things today any more than they did in Jesus' day. So what! People got saved, sold out to follow Jesus with 100% of their being and some died in the faith and went to Heaven. The critics rarely had any folks saved under their criticism. Interesting isn't it?
So the point of this rant is this. If God had called you to write Christian Sf, WRITE IT WITH ALL YOU'VE GOT!
If people criticize you and tell you ( as they've told some of my brothers and sisters on the Sandbox) that "when you mature in Christ you'll stop that and write devotionals and self help books." (nose in the air tone of voice) IGNORE THEM AND OBEY GOD. Remember they told Jesus he couldn't heal on the Jewish Sabbath day, or preach the things that he did. The same crowd told the disciples that they couldn't heal and preach in Jesus' name after he was safely crucified.
If they tell you that Fantasy isn't Christian (Um, Mr. Lewis, sir. Do you know that you were writing pagan literature all of your life?) DON'T LISTEN TO THEM! If that's the genre God inspires you to write, then write it to the Glory of God and try to reach some of the ones who will never come to church and read any of the "Sanctified Christian books".
Just heed Jude's admonition (did you notice that he was one of Jesus' natural half brothers, one of Mary and Joseph's sons) to "Pray continually in the Holy Ghost and thus keep yourself in the Love of Christ (keep that flowing through you as your driving motivation for everything you do)"
Go in the Spirit; act out of his burning love in your heart and you will fulfill his will to reach the lost with his Message. Believe it, count on it as His promise and do it with the strength he alone gives. Don't be detered by the critics. Many well meaning, but fallible men and women may oppose you but you be faithful to your heavenly vision.
Write on Brothers and Sisters
Take the Gospel seed to the deepest hell of human experience and intellectual / Cultural darkness in faith; then watch Jesus' light spring up and blossom into eternal life out of the manure pile of our dying ways. Sow on and don't be discouraged, your labor of Love will yield salvation for others and glorious Joy in Jesus for you.
Many times the most despised and shunned gospel messengers have been the most effective for eternity.
The Holy Ghost to inspire you
God's word to guide you
God's hand to hold and preserve you
God's Joy to give you strength
God's Son to anchor your faith
God's Corner stone to guarantee your inheritance in Heaven
God's Love to control your feelings, thoughts and actions
God's Own heaven to draw you homeward
God's Grace to give you all things you need for this world and the next
These things be yours and make you fruitful in the Ministry He has given you to fulfill.
Write on
Sola Gloria Dei (May all Glory belong to God who alone is worthy)
Yours by his Grace Alone
dave