Movement
Different blocks have different walking/running speeds, encouraging the creation of roads. Also, leather and especially metal armor slows down your movement speed and increase hunger gain.
Crafting
Crafting recipes would stay mostly the same, perhaps with some nods to sanity like making wheat and seeds the same thing and requiring an oven to bake bread. However, there are two major changes: having to buy most crafting recipes with XP, and a quality metric for crafted items.
Low-tier crafting recipes such as wooden tools and simple foods are immediately available. All other crafting recipes require a cost in XP the first time they're used. This XP cost is higher for fancier recipes.
This basic crafting creates low-quality items. These perform worse than standard: tools take longer to break blocks, weapons do less damage, food reduces hunger less. They also generate less XP. (More on that below.)
You can upgrade your skill at a particular recipe for a larger XP cost, which allows you to create standard-quality items. These are like the current items in Minecraft.
Specialization
Finally, for a large chunk of XP, you can choose a specialization that allows you to create high-quality items of certain types and/or has benefits in other ways. Only one specialization can be active at any point. The aim of this is that, in multiplayer, players can specialize in particular tasks. From this specialization, trade arises, and from that, more complex social structures. So instead of doing everything yourself, you might specialize in smithing and trade with a nearby player who's specialized in farming.
Some possible specializations:
- Miner: Increased mining speed.
- Woodworker: Crafting recipes for wooden items yield extra output.
- Warrior: Additional damage, less speed decrease from armour.
- Scout: Faster movement speed, decreased falling damage.
- Farmer: Harvesting plants yields more food. Bonemeal more effective.
- Cook: Crafted food decreases hunger more and produces more XP.
- Fisherman: Fishing rods work faster and produce better outcomes.
- Smith: Able to create high-quality tools and armour.
- Butcher: Animals killed yield extra items.
- Enchanter: Enchanting items has reduced XP cost.
- Wizard: Can duplicate magic books.
- Trader: Gets better deals from trading with villagers. (See also my post on better villagers and trading costs.)
etc.
XP
This is probably the major change, and something of a hobby horse of mine. The way you gain XP is completely replaced. Instead of gaining XP by killing stuff and mining, you gain it by doing new, different stuff:
- Eat a new kind of food, especially high-quality items.
- Kill a new kind of enemy.
- See a new kind of block, item, or mob.
- Use a new tool or wear a new item of clothing, especially high-quality items.
To assist with this, a large number of new but straightforward content is added: lots more flowers, animals, food crops, etc. Additionally, there's some new types of stuff entirely used for decoration and XP gain. In particular, fossils and cloth-based clothing would be cool.
So to be able to unlock crafting abilities, improve your crafting, and ultimately choose a specialization, you need a lot of XP. And you get that by getting these new experiences. And guess what - this means these experiences now have a trade value as well! As a cook, the major value of your food over generic food is that it causes much more XP gain. As a scout, you can make your living by gathering unusual plants and items and charging admission to see your newest collections. There could even be a specialization for this: a curator, who can put items into picture frames that cause better XP gain.
Intent
All of these proposed changes are in service of the same intent: creating mechanics that encourage the creation of societies in multiplayer. Interdependent societies with road networks, trade, perhaps even guilds, contracts, banking, and so on.