Even if this is true, the Swede player has invested 33% more ressources and 37.5% more population space. Winning that fight seems to me relatively fair in that case, especially when you consider the Hakkapelits bypass both the melee multiplier and melee resistance of the Sepoys by staying in range mode.
Technically, that scenario (Hakk VS range heavy infantry) is the only one where Hakkapelit has a huge advantage over similar heavy cav.
Mathematically speaking, there is nothing on Hakkapelit that would give them an edge in those matchups. Outside of that weird range attack with splash, they have basically the same stats as Uhlans (main difference being extra HP for Hakka but way better armor for Uhlan, i.eā¦ 30% VS 10%).
I fail to see what kind of micro you could use with them when facing units like Zamburaks that have more speed and range.
Go melee against Light Cav? No better than Uhlans on paper.
Go range against Light Cav? Your lower damage now does splash damage, but is reduced by the light cav armor.
Maybe some video would enlighten us.
Because if you are right then Hakkapelit counter basically everything except heavy cav, so this would be by far the most OP unit in the game.