Make more trading possibilities for the villagers

I love the many different trades that villagers can trade. Whether it being how I can trade away the excess string, wool, wheat, or other things you would get abundance of to being able to get rare things through some villagers, I think the trading system at least has a reason for people to use it. The only thing I want more of, is more trades of things we get abundance of, for example, one material I still mine but don't use it much is copper, but I can see a villager wanting copper and trading it for emeralds like how there is a trade for coal to emeralds or iron / diamonds to emeralds.