Why is your argument based on necessity? There is no indication in Revelation 20 that this "a thousand" years symbolizes time. Both points are your opinion. If we take another verse in Revelation like Revelation 13:5
"And there was given unto him a mouth speaking great things and blasphemies; and power was given unto him to continue forty and two months."
Is this also just symbolizing TIME in which every person lives? How can you just arbitrarily decide which amounts of time given in Revelation fit your symbolic criteria?
What is written proves itself that "a thousand years" equates to time when faithful saints are alive on this earth before they physically die. John is NOT seeing resurrected physical bodies that have lived and reigned (past tense) with Christ for ONE thousand literal years. Because NONE will be physically resurrected before the last trumpet sounds. Thats the seventh trumpet which sounds "there should be time no longer." (Rev 10:5-7)
Therefore, John is given to understand the souls of humans who had already lived and reigned with Christ in time (a thousand years) are not dead but are spiritually alive in heaven being faithful unto death, so they received a crown of life, just as Christ told John to write they would.
Here is another symbolic reference to time found in Revelation. When John writes of being tried and having tribulation for ten days, it does not equate to exactly TEN literal twenty-four-hour days. Ten is referring to fullness or complete IOW in this world many saints will be called to physical sufferings that will lead them unto death. But instead of physical death destroying, the faithful saints receive a "crown of life."
Revelation 2:10 (KJV) Fear none of those things which thou shalt suffer: behold, the devil shall cast
some of you into prison, that ye may be tried; and
ye shall have tribulation ten days: be thou faithful unto death, and I will give thee a crown of life.
This is how John can see (understand) there is still a living soul (spirit) in heaven of faithful saints who have already lived and reigned with Christ in time (a thousand years) who were faithful unto death. Their physical body returned to the earth, and as living (spirit) soul they ascended to heaven to be with the Lord until time given this earth should be no longer. (1Cor 15:44)
When we continue to read in context, vs 6 shows us that others John writes are blessed and holy, hath part in the first resurrection, no fear of the second death, but they shall be priests of God and of Christ and shall reign with him a thousand years. IOW it's not only the saints who were beheaded for their faith that shall reign with Christ in time (a thousand years). The full number of all who shall be spiritually alive as living souls in heaven after physical death, must first be born to reign in time (a thousand years) with Christ. Both those who have already died in Christ, having already lived and reigned with Christ, and those who shall in life reign with Christ, are faithful saints during their lifetimes, that John writes are a thousand years. If a thousand years does not equate to TIME given mankind on this earth to be born again in Christ, how can this time be already past for saints who have physically lived and died, but also future for those who shall be found of faith in Christ?
Revelation 20:4 (KJV) And I saw thrones, and they sat upon them, and judgment was given unto them: and
I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received
his mark upon their foreheads, or in their hands; and
they lived and reigned with Christ a thousand years.
Revelation 20:6 (KJV) Blessed and holy
is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and
shall reign with him a thousand years.
As I've said, the text itself PROVES a thousand years equates to TIME given this earth to bring forth fruit as the Gospel of Christ is proclaimed unto all the nations of the world, and whosoever during their lifetime lives and reigns with Christ (believes in Him), HAVE eternal spiritual life with Christ in heaven after their bodies have physically succumbed to death.