When testing the Mexican Revolution, unique to Spain, I noticed a small, but odd thing.
One of the Mexican unique units is the Vaquero, which is an unit visually identical to the Comanchero and with almost the exact same HP and attack stats. The only notable difference between the two is that the Vaquero can build livestock pens, gather food from livestock and only cost 1 population, while the Comanchero can’t and cost 7 population.
The odd thing is that despite being basically the exact same unit, the Vaquero doesn’t replace the Comanchero. Many other revolutionary nations have similar units(Cowboys, Jagunços, Morochucos, etc.) that do replace the Comanchero when revolting, even the other Mexican unique unit, the Chinaco, does replace the Renegado when requested from the home city. It seems that the Vaquero is the only odd exception to this rule.