This guy did it
Offers greater range of values for the battle size setting. Game's range is 200-1000, this mod allow you to expand it.
www.nexusmods.com
He even referenced this thread lol
The main issue is the 2048 hard cap. Since cav units count as 2 units in the engine, the largest "safe" number to run without crashes is 1024.
This is no problem if you stick to infantry/archers in custom battles. But in single player you can't predict army composition so any battle could crash you if you're out of the safe range.