WARNING: I used google translator and there may be errors in the text
here are the ideas:
1)add factions like :Holy Roman Empire,British Empire,France,China,Kievan Rus,Vikings
2) make each faction unique abilities, technologies and weapons, for example, China's Hwacha or Britain's Scandinavian and French ships that bombard the enemy's coast
3) Add Elephants to the game (maybe they were all used but I'm bad at stories) and pigs which can be set on fire and scare the elephants
4) add an easter egg to the game for revenfield type: the machine gun of which you can get by doing a whole quest
5) add the voice acting of the characters under the language of each faction, for example, as in Kievan Rus, the Russian language with obscenities (your fans will help in the voice acting and translation) and they will sound when, for example, they wounded or killed someone from the detachment
6) add a squad mode like in Revenfield