Proposal to change 2 links on the page Project:About
You are right: "translatewiki.net languages" is supposed to be a guide to the processes related to the support of languages specifically on translatewiki.net. I like your ideas on expanding the page, and hope that you will make some amendments to the page - as I've commented, editing your own work is not an easy task. I'm not convinced about chopping the fallback language section. I think documentation on fallback should be on a page which might eventually qualify to be localised. FAQ can't be localised, because it changes too often. I prefer improving the fallback section so that it's as good as or better than the section on FAQ. But it doesn't have to stay on "translatewiki.net languages". If there is another page where it would fit, it could be moved there. However, I take your point that the link from Project:About would be better staying to the fallback section of the FAQ page.
With regard to changing the About page, this would have been revised and updated a long time ago, if it weren't one of the pages already set up for translation. That's why I suggested changing two already existing links which could be done by a bot perhaps, or even manually by myself on all languages, without having to bother the other translators. So, I like the idea of summarising the "translatewiki.net languages" page on Project:About and adding a link, and would be glad if you could do this.