It's definitely possible. I got a decent time on deity for this past week's, something like 18 turns, and I could have shaved it down if I kept at it. I can't remember the whole sequence of moves, but I started by settling on the southern coast and using the great explorer's gold to rush a galley, sending that east to get the knights templar, then floating the knight south and capturing the first capitol. Next I walked him west and took Rome. Finished it with horsemen armies, but I lost a few due to poor planning so I could have definitely done it faster.