Teaching Villagers

One of the biggest metas in the game has been a trading hall, a way to get max gear relatively easily, albeit with a lot of time needed in order to achieve. All of us have done it at this point. HOWEVER, this came with a large wave of pushback from old-school players, because it's too easy or because it completely gets rid of the adventure aspect of the game. 

SO what if we allow the trading hall to remain, all while keeping the adventure aspects. First, nerf trades, maybe remove the good ones, What if, after maxing out a librarian, you can interact with a lectern and place a mending book (or maybe even a number of books/other materials depending on how strong the enchantment is) that you found in a dessert temple and with a diamond or two to motivate him, and boom he has a new trade. Limited to one per villager for balance.

Maybe the mending book requires a bottle o enchanting, luck of the needs rabbit foot, fire aspect and fire charges or unbreaking calls for ancient debris. Maybe there can be brand new items specifically for the new trades, similar to the new recipes for armor trims (more expensive obviously) The possibilities are endless.

Obviously I'm not a game dev so some of the prices, possible xp involvement, or even the idea of letting you teach each villager type new things to balance out the feature is all subject to change from you guys, but overall I feel this, or a something similar to this could make the trading hall issue less prevalent.