This is my story of Epic 37 from Realms Beyond Civilization. The scenario setup is there, although it isn't much. Deity difficulty, you play as the Iroquois, and all your opponents start in the middle ages.
This called for some pre-game strategizing. Sirian wrote in the info page that we've been given a good ancient Unique Unit, and we may need it. However, I think this is a red herring. With the middle-ages start for our opponents, every civ's starting units will be archers and spearmen, and Feudalism for pikemen is right around the corner if they don't already have it. The only possible Mounted Warrior strategy is a rush with maybe twelve units out of three cities, and that's if we can find horses.
So, I think it's more likely for a builder plan to succeed. Priority One is to get into Republic as soon as possible, and ride the cash generated by that to Priority Two, getting up into the tech brokering loop.