Agreed. Kublai Khan leading both China and Mongolia is a good example of when this works. Alexander leading Persia and Egypt is definitely not the way to do it.Although I agree with the first part, I do still see a lot ot potential and value in alternate leaders where they are appropriate, and do not feel that every leader needs their own, separate, and distinct civ cooked up, in many cases as a conttivance.
I also agree about the last part. One thing I absolutely hate about Civ is when they make a civ that is basically made because they wanted a certain leader in the game. Macedon was not a Macedon civ, but an Alexander the Great civ. And Gran Colombia was a Bolivar civ. And in Civ V the Huns were an Attila civ. And in civ IV Holy Rome was basically a Charlemagne civ. Yes, there are lots of interesting figures in history that could've been great leaders for Civ, but if there is no civilization they can lead, just make them great generals or something, and move on. For this reason I don't want Tamerlane as a leader. What civ will he lead? The Uzbeks? This is kind of a stretch, just like Nzinga Mbande leading Kongo. The Timurids? Who are the Timurids? Are they a nation? Is there a Timurid ethnicity? National identity? Culture? Language?