> But for a plugin system, many people would prefer to write plugins in JS itself, so for WASM plugins, they might have to be compiled to WASM first. Dont know how if there is a mature implementation of JS->WASM.

Not everyone tho, which is kinda the point of abstracting away your language for plugins. People like Python, Lua, Go, Rust, etc... Some do like JS of course, but not everybody. Re: mature implementations, I would guess worst case QuickJS probably can compile to WASM and it's small enough that your runtime will probably offset the extra blob size.