Finally I can upload some usable code here, in this case to be able to
load and manage fonts for languages with non-Latin scripts, through
babel and fontspec (in LuaLaTeX). It is an attempt to simplify from Org
the multiform syntax of babel + fontspec. Of course, it is more limited,
but for regular use I think it may be enough.

Since this code is mostly a proof of concept and the names of many
things (and the things themselves) are still tentative, I thought it
would be more useful to attach it in an *.el file, rather than a regular
patch. Loading that file everything should work fine. I also attach an
org document with some examples of use. In any case, there are more
explanations inside the .el file.

One of the big problems I have encountered when trying to create a
"(LaTeX) Babel interface in Org" is the *horrible* multiplicity that
Babel has for language names. That is the reason for the :babel-alt
property in 'org-latex-language-alist', which collects the names that
babel supports for \babelprovide, which are not always the same as the
'classic' babel syntax.

Finally, I find this way more useful (that is, loading fonts with
language support), instead of a fallback font system based only on the
Unicode scripts. It is less 'automatic', but more precise, and it also
does not require much 'specialized' intervention on the part of the
user.

Best regards,

-- 
Juan Manuel Macías

https://juanmanuelmacias.com

https://lunotipia.juanmanuelmacias.com

https://gnutas.juanmanuelmacias.com