Fields of Study: an Experience and Enchantment rework.
Experience is an interesting thing in Minecraft, it's different from other games because it's not just a reward or measure of your progress, it's actually the experience you gain by living and doing things. And the enchanting system reflects this, by either having you write down your experience in books or modify and fine tune your equipment using the experience you've gained.
The only problem is it kinda sucks due to it being a neglected mechanic that the developers don't seem to have a unified idea of advancing. I'm suggesting a relatively simple change that would have a cascading effect of making experience and enchanting more fun to utilize rather than a chore to get useful lategame gear.
That change is Fields of Study: different types of XP you can get for different tasks.
These fields of Study would be Labor, Wealth, Magic, and Combat, and each one would have a color associated. Labor would be green, wealth would be yellow, magic would be blue, and combat would be white.
Your XP bar, while still measuring level based on total Experience Points, would be the color of the culmination of your total experience tallied up, being biased towards the colors on the gradient. Basically, if you're bar is an intense singular color, it means you have a lot of one kind of experience, if it's a shade between two of them, it means you have a lot of two kinds of experience, and so on.
Different kinds of XP are awarded for different tasks, some tasks awarding bonus XP in a different field, like mining certain ores awarding both labor bonus wealth, for instance.
This would also have a bit of a cascade effect on enchanting, enchantments would each be classified as one of the four fields of study, each enchantment in the table would be one of the relevant colors, helping reduce but not completely eliminate the RNG of the enchantment table. This also means you wouldn't be able to get enchantments from different fields in the same roll, like Efficiency V and Fortune, for instance.
Enchanting would cost 1 lapis per roll to compensate. This also has the side effect of making enchanted books a decent medium for storing XP, at the cost of the lapis, though.
Combining and repairing tools in an anvil would only use labor experience, but combining books would require experience in the relevant field.
Bottles O Enchanting would give random XP.