What mods what you like to see that are silly? Nonsensical mods etc.
A Perfect example: Elephant Trebuchet Mod.
You mean a hypothetical one or something that already exists?
Idea for mods. So, think of something. But silly ones.
A Llama Monk that can go round converting animals. Including wolves, lions etc which can be used as part of your army.
Unit and tech shuffle. They are created in different places. May reshuffle with age up. Upgrade knight at the monastery? create trebuchet from the barracks?