Challenge sounds interesting as start location does have a lot to do with how you may or may not proceed... I've done this a few times w/ Mehmed now (playing through about 1700 each time) and Nappy once. I did Nappy on Warlords as well. Couple quick observations. Prince, Continents, Epic speed.
* I tried using GSs to do a south route. Got GP around 900 w/ Liberalism (not so good), but did have Construction, MC, Machinery, and CS before GP. Very tough avoiding Fishing to keep the south route open especially given 2 of 3 leaders are Organized and always seem to get coastlines with fish. Janissaries very effective, period lasted about ~ 300 years. Wiped two civs in that time frame. W. proper seige, Jans lasted longer. AI had issues getting Grens up and running fast even after it had Chem. Organized is a nice benefit to keep your economy running.
* Tried pure north route, GP around 720. Did north route exclusively. Was very easy to conquer English (all LBs) and got through a lot of Huanya. AI seemed late with Chem or Rifling this time despite somewhat fast techers (Hannibal, etc.). After awhile the sheer amount of LBs in cities was making it difficult to plow through. LBs in a relatively small number are not so bad, but once the AI ramps up and LBs get 2 promotions it does get tougher.
* Nappy, best run yet. Again, got through North route. Did have enough wonders (Stone close by) to generate GEs, so going to give that a try. Again, 1200s, Grens start to show up in small numbers. A lot of good techers here and a vassal state kept me from getting through 2 civs.
One thing I wanted to reiterate from others: you need to build seige ahead of time as you waiting to tech to Muskets. Though I did find a couple cities w/ Archers/etc., the AI was able to get LBs in place quickly. My Nappy location wasn't good, so cities couldn't handle extensive drafting.
(on warlords 2.08, with creative giving half priced libraries, louis could be the best one)
I too agree that Louis may be best for this. Industrious will also get you the wonders to generate more GEs. Onto Nappy on vanilla, Louis, and some pure south route testing.
In sum from testing, the north route seems best because you get better trading techs and it provides infrastructure bonuses and benefits that you may not get by focusing hard on the south route. I do think w/ Warlords you can generate enough GEs (w/ appropriate from others) to get it done. Will post if find anything interesting.