It's interesting that the phrase "civil service" or "civilian service" is not found in the NWT. The closest thing is "public service" which is translated "holy service" at Luke 1:23.
Daniel worked in a government position. So did Esther, Mordecai, Nehemiah, Ezra, Joseph, Solomon, David, and many others. In some cases, they were directly appointed to that public service by Jehovah.
No where does the Bible say "you may not work in civilian service" just like no where does it say "you may not vote". When the Bible says "you must be no part of the world" it's not referring to civilian service. It's referring to not acting like Satan, a person who is hypocritical. When the Pharisees were figuratively striving to have a clean outside of the cup but were inside full of dead men's bones, Jesus called them sons of their father the Devil. Those men were part of the world because they preferred the way of hypocritical showy display instead of the way of love.
Voting doesn't make someone part of the world. Holding government office doesn't make someone part of the world. Having a political party card doesn't make someone part of the world. Being a religious hypocrite does make someone part of the world.
In context, when Jesus was talking about being "no part of the world" he wasn't talking about voting. Jesus mentioned Judas, who was a religious hypocrite. Judas pretended outwardly to love Jesus, but he really loved money more than he loved truth.
John 17:12-16
"When I was with them, I used to watch over them on account of your own name, which you have given me; and I have protected them, and not one of them is destroyed except the son of destruction, so that the scripture might be fulfilled. But now I am coming to you, and I am saying these things in the world, so that they may have my joy made complete in themselves. I have given your word to them, but the world has hated them, because they are no part of the world, just as I am no part of the world. “I do not request that you take them out of the world, but that you watch over them because of the wicked one. They are no part of the world, just as I am no part of the world."
In context, when John was talking about being "no part of the world" he wasn't talking about civil service. He was talking about "antichrists", people who once were Christians but whose actions showed they didn't really have love for God.
1 John 2:15-21
"Do not love either the world or the things in the world. If anyone loves the world, the love of the Father is not in him; because everything in the world—the desire of the flesh and the desire of the eyes and the showy display of one’s means of life—does not originate with the Father, but originates with the world. Furthermore, the world is passing away and so is its desire, but the one who does the will of God remains forever. Young children, it is the last hour, and just as you have heard that the antichrist is coming, even now many antichrists have appeared, from which fact we know that it is the last hour. They went out from us, but they were not of our sort; for if they had been of our sort, they would have remained with us. But they went out so that it might be shown that not all are of our sort. And you have an anointing from the holy one, and all of you have knowledge. I write you, not because you do not know the truth, but because you know it, and because no lie originates with the truth."
The GB loves money more than they love truth. They have a form of godly devotion, but prove false to its power, just like it says in 2 Timothy 3. They are part of the world of their father the Devil, and they act like their father who also pretends to be an angel of light but is actually full of darkness. They are religious hypocrites.
The GB misapplies the Bible's words about "no part of this world."
Romans 13:4 makes clear that it is with God's approval that some "bear the sword." "The existing authorities...for it is God’s minister to you for your good. But if you are doing what is bad, be in fear, for it is not without purpose that it bears the sword. It is God’s minister, an avenger to express wrath against the one practicing what is bad."
Cornelius was an army officer. The Bible calls him "righteous". While he was an army officer, an angel came and spoke to him. While he was an army officer, he received holy spirit and was baptized. The Bible doesn't say that Peter came and said, "Hey, Cornelius, you have to repent of being in the army. You have to quit your job." Nope. Cornelius, the army officer, the righteous man, was qualified to receive holy spirit and be baptized while still an army officer. He was no part of the world even though he was part of the military.
In context when Jesus told Peter to put down the sword, it was because at that time it was God's will for Jesus to go through the unjust arrest. If Peter took up the sword at that time, he would have been killed by those other dudes with the swords.
We know Jehovah hates violence, but that doesn't mean that he's displeased with all the men who bear the sword. To the contrary - the governmental authorities stand in their places at present with God's permission for a purpose in harmony with God's will. God will discipline them at the proper time, and any who abuse their authority will receive their wages for such abuse. But the righteous ones among those in the military and the governing authorities will receive their reward for their righteousness, just like Cornelius did. There are many many loving, good people in the military and among the governing authorities. It's not a sin to be in civilian service.
Ecclesiastes 3:1-8
"There is an appointed time for everything,
A time for every activity under the heavens:
A time for birth and a time to die;
A time to plant and a time to uproot what was planted;
A time to kill and a time to heal;
A time to tear down and a time to build up;
A time to weep and a time to laugh;
A time to wail and a time to dance;
A time to throw stones away and a time to gather stones together;
A time to embrace and a time to refrain from embracing;
A time to search and a time to give up as lost;
A time to keep and a time to throw away;
A time to rip apart and a time to sew together;
A time to be silent and a time to speak;
A time to love and a time to hate;
A time for war and a time for peace."