Villager Quests to Earn Discounts

When a player performs a quest for a Villager, the player's reputation with that Villager improves, allowing the player to spend fewer emeralds when buying from the Villager.

This would be done through the existing gossip system. The discount would decrease over time, and other villagers who have gossiped with the villager for whom the player did the quest give the player a (lesser) discount, which also fades over time.

To enter a villager's quest GUI instead of his trade GUI, hold sneak and right click him.

To accept any of the offered quests, select one or more checkboxes and click the "accept quests" button.

Each quest will be something very very simple like Mine 2 Deepslate, or Place 3 Dirt, or Kill 4 Zombies, etc.

When the player accepts the quests, the villager looks at the player's statistics and memorized how many times the player has previously done each task.

When the player later enters either the trading or quest GUIs, that villager takes another look at the player's statistics to see which quests, if any, the player has completed.

Extra rewards for success are experience points for the villager and the player.

To make quests riskier, the player must give the villager a deposit of one level of xp, which is payed back on quest success.

Each Villager generates a new random quest each time he renews his trades.

Quests older than a Minecraft week expire.

If a player has accepted a quest from a villager and it expires without the player completing it, the player loses a small amount of reputation with that villager... half as much as he'd have gained for succeeding.

Each world or village has a quest table. Each entry in the table is something like (mine cobblestone, repeat 3, reward 5). When a quest is completed, the reward decreases by 5% and the repetition increases by 1. When a quest expires, the reward increases by one and the repetition decreases by 5%.