Outside of the "timestamps" of "soon", are there any indicators in the book of Revelation that its past history? I think the best argument for your view would be not the "soon" statements but the "Five have fallen, one is... one is yet to come" etc. of John. Because a man's lifespan is only so long, which means the 8th king must of happened in the first or second century.
Btw: What about Revelation 20? Are you amillennialist or premillennialist or panmilennialist?