Ok I have a better undesrtanding now.
This modification requires extra work about the documentation and fast install script
https://github.com/mycozycloud/cozy-setup/blob/gh-pages/install_cozy.sh

I will merge your PR once we'll modify all this stuff. As reminders I add in the following what should be changed:
https://github.com/mycozycloud/cozy-setup/blob/master/README.md#how-to-install-cozy-on-your-server
https://github.com/mycozycloud/cozy-docs/blob/master/src/documents/host/install.html.md