Some ideas for large projects. You can post more if you like or discuss previous ideas.
1: Sugar Gulag
A village surrounded by sugar farms so big parts can grow back while you harvest other parts. In the village you turn the sugar into paper and trade the paper for emeralds, and all villagers who don't trade paper are killed.
2: City of Music
Should have a moderate density of villagers and be filled with pressure plates in random locations connected to note blocks, so that music is constantly played by walking villagers and players.