I’m not clear on who is supposed to do the translating that isn’t doing it today, or why the mapped IPv4 addresses don’t qualify. Virtually all ISPs either give you an IPv4 address or do the translation for you, and the software you write doesn’t have to care exactly how it’s set up for the most part (there’s some subtlety about stuff like MTUs, but if you’re just doing unencapsulated TCP it usually doesn’t matter). It can just use whatever comes back from DNS (including using the official mapped addresses if only an IPv4 record exists) and expect the network stack to figure it out.

None of this stuff works perfectly, but it’s powering almost every mobile internet connection in the world so I don’t understand what is missing.