Ideas to Maybe Eventually Get Around To At Some Point

Unnamed RPG Game

Just an excuse to write a mostly-functional game engine from scratch with decent 00's-era hardware compat

• Actually working on it, though still very early

Voxel Game

Minecraft is proprietary and has to juggle both the preferences of a large playerbase and development time. Minetest is open-source (LGPL2), but suffers from engine limitations that make certain things difficult or impossible. (I also don't personally agree with their current design philosophy)

Ideas

• Simple and robust decentralised multiplayer protocol (Ideally over UDP, though WebRTC, WebSocket, and TCP are also possibilities)
• Pubkey-based auth (Minecraft requires an Xbox account, some games opt for server-local account registration, and some require an account on a big master server like ClassiCube and Veloren)
• Custom serverside extensions (new blocks, entities, sounds, etc.) that don't require anything more than a vanilla client
• Try to stoke independent client and server implementations (ClassiCube's protocol has a small handful of client and server implementations, though the ClassiCube client and MCGalaxy server currently dominate the scene)
• "Infinite" world size (Ideally cubic but I can live with a height limit)
• Try to make the most out of network bandwidth, clients can parse heavily packed data structures way faster than the network can send easy-to-parse unpacked ones
• Pull-based rather than push-based protocol (ie clients request data rather than the server throwing it at them and possibly dropping the packets)

Tiny Embeddable WebAssembly Library

Theoretically possible, although WASM binary modules are a pain to parse

I've already written most of a non-verifying WASM interpreter in Rust

Danelaw

Roguelike set in Danish-ruled England

QuakeWorld and ClassiCube Crossplay Proxy

Theoretically possible