While reading Byzantine Armies 1118–1463 AD I became inspired to do a mod about it, because so many mechanics in this game would suit it well.
So, this mod would start in the year following the chaos the Fourth Crusade, most of the Byzantine territories are in a state of disarray. In addition to the main kingdoms, many despots and Latin adventurers have seized chunks of the realm. The next forty years would truly be a warring state period.
More precisely it would begin on 20 March 1205, the day after Battle of Adramyttion, where the first Nicaean Emperor likely died, leaving the empire in the hands of ambitious Theodore I Laskaris. Meanwhile, the first Latin Emperor was likely murdered in Bulgarian captivity a few months prior, thus Latin Empire too would have given to a determined man, Henry of Flanders.

So, this mod would start in the year following the chaos the Fourth Crusade, most of the Byzantine territories are in a state of disarray. In addition to the main kingdoms, many despots and Latin adventurers have seized chunks of the realm. The next forty years would truly be a warring state period.
More precisely it would begin on 20 March 1205, the day after Battle of Adramyttion, where the first Nicaean Emperor likely died, leaving the empire in the hands of ambitious Theodore I Laskaris. Meanwhile, the first Latin Emperor was likely murdered in Bulgarian captivity a few months prior, thus Latin Empire too would have given to a determined man, Henry of Flanders.
- The map (as seen above) would center around Constantinople, span from Hungary to Egypt and from Rome to Lake Sevan. But also include the surroundings of the Black Sea.
- At least Venice, Genoa, and the Mongols would be represented as off-map powers, much like China.
- The provinces would be quite small, and the impassable terrain would render certain areas strategically defensible.