The goal is certainly worthwhile and I'd certainly support: just think how many editor-hours are "wasted" on producing audio files for a limited coverage, when the simple cases could be automated and users could focus their efforts on the difficult cases.
However, to support a project I need to know what the project actually entails and how it will be made viable: https://www.mediawiki.org/wiki/Extension_talk:Wikispeech
Nemo