I think any ORG leader in charge of Sumeria would be a cool idea. Fast (at priesthood), super cheap (effectively 45 hammer) courthouses, and half civic upkeep at all times. Such an easily placed early boost (cheaper than granaries...) could help you REX or conquest like a monster with much more reckless abandon. Probably best paired with FIN to take advantage of the extra commerce freed up to go towards science, or AGG/CHA to leverage the Vulture as much as possible for aggressive expansion early so Darius or Hammi/Napoleon.
I just realized it's much easier to think of UU combos, espcially involving tossing in the normally shafted Boudica into a position with a better (early) unit to use:
-Tokugawa of England for some seriously scary Redcoat drafting. Maybe Boudica too, as a change of pace from Churchill.
-Shaka/Boudica of Inca for double promoted Quechas (if it works that way). Shaka gets the Terraces in place faster for more 2nd ring settling and faster whips too.
-Huayna of Carthage or Portugal on a water map would be seriously frightening. Bismarck could also go for a traderoute heavy strategy with GLH with his EXP trait speeding up Cothons. Rosie is still better at getting GLH itself though. hard to beat IND/ORG + Fishing for that.
-Churchill of Mali. Skrimisher rush everybody! Qin or Mao could also be used, but China's UU is already better assuming you can get to Machinery quick.
-Boudica of Rome for super powered Praets. She might also do okay boosting Maya's Holkans since they are resourceless and can combat warriors, chariots, and horses as well as archers. Scarier than Quechas?
-Lincoln of Egypt. Get a couple super early Great Prophets (however useful those are outside of Religious games) and get those War Chariots promoted up faster.
-Hammi of Holy Rome. Actually make HRE not suck with great starting techs, boost up the UU and combine ORG with the sick, sick Rathaus.
-Church of Spain. Not gonna lie, this pretty much just revolves around faster Citadels for super powered Trebs/Cannons.
-Hammi of Zulu, mostly taking advantage of Ikhanda + ORG trait, though AGG helps build them and boosts early melee units for rushes. Hammi seems to be a good candidate for improving other civs at least a little bit, his combo of a war trait and economic trait applies a lot.
There's probably a quite a few more extensive ones.