How to keep running a “multilingual” WordPress blog without multilingual plugins

I have found (I think) a way to migrate one EXISTING, bilingual WordPress install with lots of content, to two independent copies of WordPress with the same top URL, that is without subdomains like it.example.com, en.example.com… but without changing the URL of any already existing page. It seems to work, but please do let me know if I missed something. Here is the detailed description of this method. Feedback is very, very welcome, no, needed!