Way of Turning Items into Experience

A way of turning items into experience would make getting XP much more interesting. Instead of going to the nether and mining quartz, players could explore, mine, or do combat, or design auto-farms. 

To make auto-farms not overpowered, but still rewarding, the more of an item that you turn into XP, the less XP that item can give, for some amount of time or permanently. This also incentivizes switching between doing different things instead of always doing what's most optimal.