EnclavedMicrostate

I can imagine a sequel set in the Taiping Civil War, contemporaneous with the ACW. The same basic campaign mechanics could apply – purchasing weapons to equip units with distinct traits, etc. – although with relatively few well-documented battles there wouldn't be as much scripting for tactical engagements. The Taiping, provincial militias (esp. Hunan) and Westernised forces (esp. the Ever-Victorious Army) all engaged in acquiring foreign arms to bolster their traditionally-armed forces, so you could potentially even have 3 distinct campaigns with different logistical challenges. Maybe it might even be possible to do a more branching campaign where you could have the Taiping rather than Qing obtain foreign support.