Hey, i think this mod is awesome, I really liked RFC and now even more with the added civs. Zulus, Native Americans, HRE, Celts and Koreans seem to be great additions to the game. I'll try them all.
However, I just played Sumeria and it isn't that challenging. It's really easy to survive the barbarian invasion and in any case, after you do if want to keep playing there's no point because the Babylonians are about to steal take all the land!! I'd much agree with SanePerson and say you use them as Israelites. Actually, it's even impossible to build Babylon (if playing the Babs) with Uruk in place because they're next to each other, meaning you'd have to raze Uruk and probably destroy the wonder there....
Oh, speaking about wonders.... Stonehenge????? I loved it! The sphynx is cool, but just keep them both! please! =)
As for the Israelites, you could give them these goals:
Keep Jerusalem until a certain date, Spread Judaism to a certain percentage, and some other thing. You could even give the Israelites a second spawn (available for players in the 600 AD scenario) around 1948.
By the way, this 2nd spawn could also be available for India in 1947 (their independence) with the 600 AD scenario, or alternatively somewhere between 1550 and 1600, when the Mughal Empire appeared.
Egypt, Greece and Rome (as Italy), could also get this later starts, with different goals obviously, and give the game more options without needing to add more civs.
Well, just some ideas!