Custom blocks via Datapacks

Please add support for custom block registration through datapacks, allowing creators to define new blocks in their own namespace, with custom models, hitboxes, and behaviour.

This would bring custom content creation much closer to vanilla systems, without requiring mods or other workarounds.

Datapacks could define blocks (e.g. `data/<namespace>/blocks/<id>.json`) with:

• A namespaced ID
• A custom model (linked to a resource pack)
• A configurable hitbox / collision shape
• Basic block properties (hardness, transparency, etc.)
• Event hooks that run functions: on_use, on_break, on_place, etc.

Why this is needed

Right now, custom blocks in vanilla servers rely on:

• Replacing existing blocks (like note blocks or mushroom blocks)
• Resource pack tricks
• Entity based systems (e.g. armour stands or display entities)

Which all have major downsides:

• They limit the number of usable custom blocks
• They break or restrict vanilla gameplay
• Entity based systems can cause performance issues and lag

Benefits

• Better performance
• Unlimited custom blocks without overriding vanilla ones
• More creative freedom for maps and servers
• Fully compatible with existing systems like commands, structures and worldgen

Why now?

With the recent changes like dialogs and the unobfuscation of server code as well as the upcoming Chaos Cubed update, Minecraft seems to give more attention to community creators. Adding the possibility to add custom blocks with datapacks would significantly expand what creators can do, without requiring mods.