How did you conclude God is busy writing names in His Book of Life at conception;
It is a logical assumption seeing that in order for man to be in a Book of Life...they must be alive, which begins at conception.
as if He has to wait and see if a child will be conceived?
The Elect are saved in the Eternal Sense in Eternity past due to God's Omniscience, however, they are not saved until they turn to Christ in faith.
The saved are natural until that time, just as men do not live until conceived.
Where does His book of life talk about conception?
It speaks of men in the womb:
Psalm 139:13-16
King James Version (KJV)
13 For thou hast possessed my reins: thou hast covered me in my mother's womb.
14 I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well.
15 My substance was not hid from thee, when I was made in secret, and curiously wrought in the lowest parts of the earth.
16 Thine eyes did see my substance, yet being unperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them.
While I would agree that God has foreknown the Elect, that does not mean we apply a designation until it is appropriate.
Concerning the Lost...
Psalm 69:25-28
King James Version (KJV)
25 Let their habitation be desolate; and let none dwell in their tents.
26 For they persecute him whom thou hast smitten; and they talk to the grief of those whom thou hast wounded.
27 Add iniquity unto their iniquity: and let them not come into thy righteousness.
28 Let them be blotted out of the book of the living, and not be written with the righteous.
We see those who the Psalmist cries out to God against...are in the Book of the Living.
Secondly, one cannot be blotted from the Book of Life except they first be in there.
And while those unskilled in the Word believe that men can lose their salvation, if they but understood that no man was Eternally redeemed until the Cross they would not make the mistake of making salvation the time one is written in the Book of Life, and the blotting out of such an one indicative of loss of salvation.
Lastly we have to consider the temporal and physical quality of the revelation that was primarily given men in the Old Testament. While David may have sought for their deaths (physical), I think we can see an eternal application to the enemies of Christ.
The Book of Life is the Lamb's book, who is Jesus, who is Christ, who is God.
The distinction of "the Lamb's Book" should be made. I do not view unbelievers, who are written in the Book of Life, to be written in the Lamb's Book of Life.
The Book has all names written of all men born alive,
And, we just saw, those who are not yet born, but are still in the womb.
and was written at the time the foundation of the world was being laid, BEFORE mankind was created and occupied the earth.
You have a serious conflict in trying to propose this, in that the Lost cannot simultaneously be in the Book...and not in the Book.
Rev.13
- [8] And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
Again, in view is the Lamb's Book of Life, and we consider the fact that this is a reference to the foreknowledge of God, for, the Lamb was not slain from the foundation of the world (though the necessity was known), but was slain roughly 2,000 years ago, a considerable time after the foundations of the world were laid. We do not simultaneously have the Son of God both creating the world while being slain.
Rev.17
- [8] The beast that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition: and they that dwell on the earth shall wonder, whose names were not written in the book of life from the foundation of the world, when they behold the beast that was, and is not, and yet is.
Again, not literally meaning they were never written in, but speaking of the fact that their perdition was a foregone conclusion from the foundation of the world.
Life begins at conception, and Eternal Life begins at conversion. Both are referenced in a past tense but we do not nullify the actual timing of the events in view.
Antichrist will not go into Hell (he is the first human inhabitant we are told of) after he is born, grows up, and rejects Christ and becomes the minister of Satan. But that does not mean that God either negated a potential for his salvation or Antichrist's responsibility for rejecting Christ. When he is judged, it will be because of his own sin, not God's.
In other words...God does not force Antichrist in the path he will take (or is taking, lol).
God bless.