1- cavalry? able to move faster and mow down ground units, weak against dragons, ogres
2- detailing? extra pretty bits for around the kingdom that give little bits of happiness to the peasants. Flowers, trees, parks,
3- schools? for children?
4- Chicken coops, lambing, cows? more animals that can be utilised for other food sources? cows=milk/meat. sheep=milk/meat/fur. chicken=eggs/feathers
5- fur and feathers? used to keep peasants warm in winter - NEED A TAILOR
6- wild animals? Hunting the wolves/deer/bears??
7 - Multiplayer mode! would love to be able to play with friends. one map but 2 seperate kingdoms that can trade and protect each other, share resources/peasants.
8 - Light sources. Fire torches that can be placed around also offering up happiness but is then a fire risk.
9 - day/night cycle - i know the mod already exists but needs 8 to make this work properly
10 - transport ships can be sent to pillage other villages off map - win or defeat. come back with coin/peasants/loot or loss of warriors
11 - war ships - archers and cannons aboard ships for defensive purposes
12 - prison - when happiness goes to low the peasants can revolt so a guard is required to keep the peace. can also use prison for raiding vikings.

i love this game and it can be amazing! I have no idea where to start with mods so i will leave it down to the professionals