C. There aren't any other languages that meet the criteria. Lua was a no-go from the start. The maintainers did not like the language, and it necessitated adding more C code to Helix which could complicate building even further. https://github.com/helix-editor/helix/discussions/3806#discu...
Rune is not mature and is developed by a handful of people. Please check the thread I linked, literally everything you could say has already been addressed.
Saying "X is better than Y" or "Why not Z?" is not constructive at all.
It is constructive, though - Lisp used to be fun when parsing complex language grammar was not as trivial as it is today. I loved it, and I worked with muLisp for many years... in the '80s and '90s. For AI (or, rather, "expert systems"), it was without a match... prior to the '80s, though. There were Lisp machines even... in the past.
B. WebAssembly is immature for developing a plugin system because of the lack of a sufficient ABI: https://github.com/WebAssembly/component-model
C. There aren't any other languages that meet the criteria. Lua was a no-go from the start. The maintainers did not like the language, and it necessitated adding more C code to Helix which could complicate building even further. https://github.com/helix-editor/helix/discussions/3806#discu...