It starts by choosing the right language for the job.
The right language for a plugin system is the one that attracts the most plugin writers. Supporting many languages is a huge boon for wasm in this department. It's one of the things that makes the JVM and .NET so appealing in the first place, but WASM is better than both combined when it comes to language selection.
> If you want a plugin-in system, maybe don't pick a language with static linking
Or… a plugin system could “just work”, without placing unnecessary restrictions on what I do.