Neat, thanks for sharing! This looks somewhat similar to Herald (https://heraldpod.com/). Herald supports custom voices for paid users, as well as forwarding newsletters and having them read aloud. What kinds of additional features are on your roadmap?
Herald turns any online content (newsletters, webpages, videos) into audio in a personalized podcast feed. You can try it for free or sign up for a paid plan to get access to more voices.