I think a 1500 launch date may well come as theoretically possible on Monarch. Unfortuantely, you'll almost surely need an improbable set of events to occur for this to place. Actually, I wonder if an OCC game on Chieftain would go faster. You might enter the middle ages a little slower (then again tech costs less, so maybe not) and you can't trade for Invention, but everything comes cheaper. So, I'd suspect a Chieftain OCC space game could go a lot quicker. Then again, getting first level techs in the modern age might work out as much harder, since you won't have cash to buy anything.
I just finished the game below. I didn't have any barbies around. I did have *mass regicide* on so that I could make early contacts and so I could delay using the luxury slider and concentrate on research. Writing started at 43 turns, I got in 30 some turns. Atlantis went wealth-worker-The Colossus. I *reloaded* a few times (random seed off) until I popped an SGL on Writing. 6 to 9 turns later I finished The Colossus and SGL rushed the Pyramids. I also ended up SGL rushing the Temple of Artemis and ended up building (I think I also SGL rushed The Great Lighthouse and bulit every other one) every ancient wonder except the Statue of Zeus and The Great Library. Someone got Invention for me one turn before I learned Free Artistry. I forgot about the commercial dock and didn't build it until I had Atomic Theory, so maybe I could have shaved a turn off that way. I also didn't have coal until very, very near the end, so I couldn't build the spaceship parts as fast I might have. I also messed up the TOE build, so that I built it like 4 turns after I entered the modern era. I got all first level techs in all three eras getting Theology, Industrialization, and Space Flight as my free techs. I've played 3 or 4 other OCC space games (where I've hand-bulit ancient wonder) where I've gifted the AIs into the industrial era and the AIs never seem to even start TOE before I get very close to the modern era. Things might go faster if I had Japan instead of Korea or Greece or Persia or The Ottomans.
I played one game where I modded the game so I could build The Colossus anywhere and tried the "parade of cattle" start. The only problem there, though, comes as that the AIs seemed to barely research any ancient level techs, so after going Writing-CoL-Philosophy-The Republic-Literature, I had to research all four of Construction, Currency, Map Making, AND Polytheism as I recall.
Playing with huts on at Cheiftain level might enable things to go faster. Oh... in the below game I timed Museum of Mausollos to finish a few turns after I entered the middle ages so I had my GA while researching Education and Astronomy.