Given that this game’s timeframe continues into the 16th century, I feel like there is potential for more firearms. I was impressed with the selection of cannons in the game, and I think this variety could be extended to infantry for some civs. Some gunpowder units I think should be in this game include…
Arquebusier
I think this unit would be good as of aesthetic change for certain civs, specifically the Chinese and Holy Roman Empire. Instead of using the handcannon the other civs use, these nations would use a matchlock arquebus to shoot at the enemy. Like the Lancer to the Knight, the arquebusier is functionally identical to the handcannonier…
OR
Another option would be if the arquebus was a blacksmith tech certain civs could research in the Imperial Age. By researching the Arquebus tech, not only would your handcannoniers replace their handcannons with an arquebus, but they would also get an increase to their range.
Petard
This was a unit in both Age 2 and 3. However, i think it should work differently in Age 4. Instead of being a unit that blows itself up like previous games, the petard would be an infantry-built siege weapon similar to the battering ram. After building a petard you will need to have an infantry unit pick it up. While a unit is carrying the petard, they can no long attack other units, but they can be directed to plant the petard on a wall or building. When a unit plants the petard, they will light the fuse and attempt to escape the blast radius, thus turning back into a regular infantry unit.
Black Riders
I remember these guys from Age 3, I always thought they were the most stylish unit in the game. In Age 4 the Black Riders would be a unique ranged cavelry specifc to the Holy Roman Empire. The Black Rider is heavily armored like a knight but has a heavy ranged attack thanks to his wheellock pistol. Range is very short though (2 tiles?). The Black Rider would be the most expensive cavalry unit in the game to balance out his strengths.
Do you have any ideas for new gunpowder units for Age 4?