Thanks for the responses everyone.
tchristensen - I was actually referring to leader traits like creative, agressive, financial, etc, not unit abilities. I will, however, say that that sounds interesting and it might be something I'd look into eventually. It's amazing how many ways people have found to alter this game and stir things up.
mechaerik - Thanks for the welcome. I've been following various threads and ideas from this site for a while, and it's a great resource of information when playing. I'm pretty much code illiterate, myself, and just adding a leader to my game was a very challenging and enlightening experience. I can see where it shouldn't be too hard to alter the traits (although I don't know where exactly, what file is that info in?), but testing it for balance and such would take a long time, and I wanted to see if someone had been through the process already.
Jarlaxe Baenre - That's one way to do it, and I could probably manage that myself. I was also thinking of a situation where each trait had a more direct impact on one essential concept of the game. One trait would greatly increase food in its cities, another would increase production (could be separated into units, buildings, and wonders if necessary), another gold, another culture, another happiness, another health, another unit promotions, another research, another great person production, etc...
Imagine a leader who had double the food and double the great person production (I know, this trait already exists), or a leader with double wonder production and double culture, or a leader with double happiness and double health!
