Flesh and blood people only appear one way, by being born of 2 flesh and blood parents.
So from a pre mill view, the saints who reign with Christ on earth also must be flesh and blood people.
And they must also have billions of babies, that is a lot of conceiving going on, and a lot of marriages taking place through many generations. Which means believers are not all changed to be like His glorious body when Christ returns, all the living raptured saints are not resurrected. They marry and have children, and their kids have kids etc...
I actually am not a pre mill. I believe all who are Christ's at His appearing and kingdom are changed to be like His glorious body.
Which IMO, break the pre-mill pov.
Philippians 3 for context on that
Our Citizenship in Heaven
17 Brethren, join in following my example, and note those who so walk, as you have us for a pattern. 18 For many walk, of whom I have told you often, and now tell you even weeping,
that they are the enemies of the cross of Christ: 19 whose end
is destruction, whose god
is their belly, and
whose glory
is in their shame—who set their mind on earthly things. 20 For our citizenship is in heaven, from which we also eagerly wait for the Savior, the Lord Jesus Christ, 21 who will transform our lowly body that it may be conformed to His glorious body, according to the working by which He is able even to subdue all things to Himself.
And 1 Cor 15 on all believers being changed at the resurrection on the Last Day
Our Final Victory
50
Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; nor does corruption inherit incorruption.
51 Behold, I tell you a [m]mystery: We shall not all sleep, but we shall all be changed—
52 in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised incorruptible, and we shall be changed. 53 For this corruptible must put on incorruption, and this mortal
must put on immortality. 54 So when this corruptible has put on incorruption, and this mortal has put on immortality, then shall be brought to pass the saying that is written: “Death is swallowed up in victory.”
55 “O[
n] Death, where
is your sting?
O Hades, where
is your victory?”
56 The sting of death
is sin, and the strength of sin
is the law. 57 But thanks
be to God, who gives us the victory through our Lord Jesus Christ.
****************
Not all sleep as in died in the Lord at His return, some were alive to be caught up together with Him in the air.
But we shall all be changed, as flesh and blood cannot inherit the kingdom of God, so there can not be a vast number born during such a 1000 year reign.
The trumpet of God sounds at Christ's return, the dead in Christ rise, and they and us still living in the flesh and blood body, we are all changed together to have glorified incorruptible bodies like He has. And then we reign with Him on the NEW earth.