In fact, I am not surprised at all.
We too modified Prestashop to use the language code in the url, added all the hrflangs etc etc.
Now our urls are all domain/xx-yy/rest of url
and in the page source code for each language there is the default and all the alternates.
(We did this before we discovered that you had made a module).
The problem I still have, however, is independent of this: I can't add Flemish because the iso code (not the lang code, the iso) is a unique field. And in fact what I'm asking you is: if you have a site where you already have France and Netherlands, iso FR and iso NL, with lang codes fr-FR and nl-NL, and you add Belgium, you use as iso "BE" and as lang code fr-BE. What iso will you use for Dutch Belgium? The lang code will be nl-BE, but the iso? That's it.
http://www.lingoes.net/en/translator/langcode.htm
Note: I have no problem buying your module if it solves my problem, but I would like to understand how it does it. I think this more a logical limitation than a technological one.
