So, a bit of a design discussion question here. Should unique units have a specialized role compared to their base unit, or should they do everything better than the base unit, thus making the base unit obsolete? And as an aside, if the base unit should be made obsolete, should the unique unit be limited in some way of how many of them can be produced?
For example, you could have a unique unit pop. The unique unit pop is increased by castles. 20 unique unit pop per castle. Unique units would consume both a unique unit pop AND a normal pop. castles provide normal and unique unit unit pop. In this way, the unique units a civ can produce is soft capped by its stone/castles.
The alternative is unit differentiation. Prime bad examples here are mongols, cumans, magyars, slavs… basically any civ that has their unique unit share a role extremely closely with another unit they have. An example of a civ that is prime good and prime bad is the romans. The romans unique unit actually replaces a generic unit (swordsman-> legionary) but the centurion with its buff aura has a completely different role than the knight line.
Mongols and the other bad civs here have their unique unit completely outclass the base unit. For example, mongol cav archers. Where are they? Nobody makes them. only mangudai. Same for magyar hussars.
Is there a name for this concept? Its so sad seeing base units getting obsoleted.
The UU doesnt have to be a better version of the base unit, and does not need to have a different usage either. It just depends on the civ design.
On open maps, you spend time in Feudal age, and often cannot afford a castle in early castle age. There you often rather use the base unit, unless the unit is straight up broken (Conquistadors) and a few units are enough to do the job, or like Huskarls (and design wise Tarkans) where youbcan produce them in base buildings (barracks/stables).
On closed maps, you can often fast castle, and many UUs can be used right away with minimal upgrades (Portuguese, Turcs), just by castle dropping. If the civ is designed to be good in this situation, it will often outshine the base unit in castle age.
Sometimes, the unit is necessary for late game (Mongols, Koreans) so you want to build castles in your base (against raids) and mass them in your late game army.
And sometimes, the UU fills the role if a couter unit that no other unit of the tech tree fulfills properly (Italians). Because the civ design is to makes the whole gameplan around this unit, so your win condition is to get to the unit (in the relevant match up) and your opponent win condition is to prevent you from building castles and transiting to this unit.
All of these are good design of UU. And UUs do not need the same purpose.
Unique units are situational. Persian war elephants can be used in a large mass to charge your opponents base when he switches to archer units. The elephants have enough hp to tank all that damage, and your opponent would have to delete his archers and make monks or halbs to counter them.
