I'm happy to address the technical part of this, but not the organizational part (finding decision makers, getting a yes/no, deciding in which shape this should be implemented).

I've created a quick hack using the client-side JavaScript (first option listed above). gzip compression brings the JavaScript down to under 500 kB. Using WebAssembly could likely improve it further but that would require more effort.

I can see if I can hack something up if there's consensus that this is worth trying, and has a chance to be added to Wikipedia as a default feature. Is there agreement that automated IPA pronunciation, based on lexconvert + eSpeak as demonstrated above, is beneficial (i.e. good enough that it's better to have it than not to have it)? If so, what's the best way to deliver a proof of concept?