Is it Possible to Cap Units

[Kurobane]

As the title says, would it be possible to put a limit on how many units that can be made. Such as 4/4 Missionary Units

 

[Lord Yanaek]

You can use the Unit_BuildingPrereqs to limit them to number/building like archeologists.
You could limit them to 1-2 per shrine or if you want a hard limit limit require the Palace as it's unique, thought that would mean only the capital can build/purchase them.