I am not a mod maker just putting some ideas here

-zombies
A zombie would only be enabled in the settings, you would have to turn { Zombie horde on } and the zombies could infect people but VERY WEAK, they can climb walls, and that stuff. about 60% of the zombies are walkers 30% are runners and 10% are dogs?

-Musket soldier
The title... A musket soldier you can train it is just like the archer but with a musket and has a bit less range and has slower rate of fire, and also has very high damage.
This would most likley be very late mid-late game so you will need alot of resourses for this.