@Paragon, I'm not saying that Ireland, Milan, the Latin Empire, the Despotate of Epirus, or the Empire of Trebizond are important enough to be represented as factions, I'm saying that pathetic as they were, their accomplishments after 1220 are still each individually greater than those of the Kwarezmians after 1220. All of them lasted at least 41 years, Ireland fought the English for centuries, Milan became a powerful and important city-state, the Latin Empire was a part of a huge amount of conflicts, the despotate of Epirus took control of most of the southern Balkans, and the Empire of Trebizond at various times expanded and contracted, while remaining relevant until the 1450's. The Kwarezmians, by contrast, existed as a vassal state for 20 years, until they were simply deemed so unimportant that even real life where there is no faction limit or unit limit they didn't make the cut. Contrasing that with Bulgaria's huge empire, or Burgundys long existance and participation as the third major power in the 100 years war totally eclipses all of these little factions, but even among them the Kwarezmian contribution was the least.
Kiev should indeed be removed, and replaced with another Russian state, or, if we do go for a later start date, maybe replaced with the White horde.
Sicily/Southern Italy did not become independant again for any length of time, being ruled mostly by aragon/spain and france after the HRE was driven out, so not only do they not exist in 1220, they never existed later either.
As for making the Kwarezmians vassals, that cannot be programmed to happen at the start of the game, and besides, the Kwarezmian contribution could be entirely summed up by giving the mongols two of their units.