Some civilizations (let’s call them “S”) have several units that automatically upgrade, whereas “normal civilizations” (“N”) do not. For instance, the Ottoman civilization has units like Spahis, Nizam Fusiliers, and Great Bombards that automatically upgrade, and the Hausa civilization has Akan Musketeers and Yoruba Cavalry that do the same.
Because of unit counters, having a diverse army is generally more advantageous—this allows you to effectively counter the enemy’s units. However, if a normal civ (N) only relies on a single unit type, it tends to lose against S. On the other hand, if N tries to field multiple unit types, it faces another problem: the high cost of upgrades, especially “Guard” upgrades in the Industrial Age. These costs can severely limit N’s military strength, leading to defeat. Consequently, whether N sticks to one unit type or attempts to use multiple ones, it remains at a disadvantage against S, which is quite unfair.
I believe the solution should be one of the following: either all units auto-upgrade, or all units require a paid upgrade. That would be fairer overall. What do you think?