How to add new house type to village?

This would be good to know, as well as making new villager type mobs / professions. 

Mobs is very easy. Return value does exist villager around

Structures you can try same way but probably won't work so you can add a mob to spawn a structure same way than above

some minor complications include its hard to add new parts to existing randomly generated structures that are groups of smaller structures: villages, end cities, strongholds, woodland mansions, etc.

and custom coding the structure will require you to be good at programming in the code editor not the drag and drop

oh and making new traders or villagers is not supported by MCreator