The biggest problem I have with this interpretation is John says the beast out of the sea is a king that "now is not", so it can't be the "one is" king at the time John wrote this - Rome. The Roman empire can't be both, "is" and "is not" at the same time.
9 The seven heads are seven mountains on which the woman sits. 10There are also seven kings. Five have fallen, one is, and the other has not yet come; but when he does come, he must remain for only a little while.
11The beast that was, and now is not, is an eighth king, who belongs to the other seven and is going into destruction. Revelation 17:9-11
The only way I can reconcile these conflicting ideas in that interpretation is the Roman empire, the fifth king, that "is" but also "is not" in John's day "is not" in the sense that it is not in the same form in John's day as it will be in the end time as the eighth king - a future form of the Roman empire, if that's what it is, that is going to be socialistic/communistic, not capitalistic, as Rome and all the world economies of history have been up to the appearance of communism in these last days.
Sorry about the length, but this is my understanding.
And the angel said unto me, Wherefore didst thou marvel? I will tell thee the mystery of the woman, and of the beast that carrieth her, which hath the seven heads and ten horns. 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, Rev 17:7-8.
And here is the mind which hath wisdom. The seven heads are seven mountains, on which the woman sitteth. And there are seven kings: five are fallen, and one is, and the other is not yet come; and when he cometh, he must continue a short space. And the beast that was, and is not, even he is the eighth, and is of the seven, and goeth into perdition. Rev 17:9-11.
The seven mountains are not literal mountains, but symbolic of present day Iraq, Iran, Greece, Turkey, Syria, Egypt and Rome being part of Satan’s ruling power found in the four nations of the Babylonian Empire, Medo-Persian Empire, Grecian Empire and Roman Empire. John would have known of all these nations throughout history and surely knew the Roman Empire in his lifetime.
The five fallen kingdoms that have always persecuted Gods people before John's lifetime were Egypt, Assyria, Babylon, Medo-Persia, and Greece. John could only know that of the Roman Empire in his life time as Israel was in subjection to Rome. Before John’s time Israel was in subjection to Greece, Persia and Babylon and in its earlier history was in slavery to Assyria and in its beginning was in slavery to Egypt.
One is: is that of the Roman Papal government up till 1798 when it received it deadly wound when General Berthier and Napoleon had abolished the papal government back in 1798 and established a secular one.
And the other not yet come and when he cometh, he must continue a short space is the reestablished Roman Catholic Church given back in 1929 when the Lateran Treaty had been signed between the Roman Catholic Church and Mussolini’s fascist Italian government. The treaty was signed by Benito Mussolini on behalf of King Victor Emmanuel III and by Cardinal Secretary of State Pietro Gasparri for Pope Pius XI. The Lateran Treaty and the Concordat unilaterally established the independent State of the Vatican City on February 11, 1929 and granted Roman Catholicism special status in Italy.
The beast that was: was Pope Pius VI (25 December 1717 – 29 August 1799) born Count Giovanni Angelo Braschi reigned as Pope from 15 February 1775 to his death in 1799. There were no other Popes until 1929 when Pope Pius XI ruled over Vatican City as he exercised principal legislative, executive and judicial power as all the other Popes have since that time.
There have been eight Popes starting with Pope Pius XI up to the seventh and eight Pope being Pope Francis. The reason Pope Francis is the seventh and eight is that Pope Benedict XVI being the seventh king (Pope) resigned. A new Pope is not selected until the former one dies.
The beast out of the earth that Satan gives power to, Rev 13, is this seventh and eight king (Pope) that will go into perdition causing a falling away before the return of Christ, 2Thessalonians 2:2, 3, as he sits on the mount of the congregation in the sides of the north taking his seat on the same mount that use to be the Temple of God as he deceives the nations claiming to be like God, Isaiah 14:12-14.
And the ten horns which thou sawest are ten kings, which have received no kingdom as yet; but receive power as kings one hour with the beast. These have one mind, and shall give their power and strength unto the beast. These shall make war with the Lamb, and the Lamb shall overcome them: for he is Lord of lords, and King of kings: and they that are with him are called, and chosen, and faithful.
The ten horns are ten kings who have not yet received their kingdoms as the Vatican's New World Order Headquarters and the United Nations Organization, One Security Council that claims authority over the world are waiting for ten permanent members. In 2009 the UNO divided the world into ten economic regions and each one will have a Jesuit Provincial set over them, but their end will come with the glory of the Lord striking them down when He returns with us His army.
Ten Kingdoms of a One World Government:
Kingdom 1: Canada, Mexico and the United States of America
Kingdom 2: European Union – Western Europe
Kingdom 3: Japan
Kingdom 4: Australia, New Zealand, South Africa, Israel and Pacific Islands
Kingdom 5: Eastern Europe
Kingdom 6: Latin America, Central and South America
Kingdom 7: North Africa and the Middle East
Kingdom 8: Central Africa
Kingdom 9: South and Southeast Asia
Kingdom 10: Central Asia