I have created several multi-language Drupal based sites and I found that for most cases, in order to implement multilanguage support, it is easier to maintain per-language Drupal sites, than one site with multilingual support.
I believe this is because the approach used by the community on multi-language support is to implement multi-language compatible features on every single module created for Drupal. I believe that with this approach there is never going to be a complete multi-language Drupal distribution because there will always be critical features missing i18n compatibility.
I propose to use an alternative approach, based on the manipulation of these elements (without interfering with drupal´s natural behaviors):
1. User input interface: Create a widget for the user to indicate the language in which his is inputting data .
2. User input processing layer: The user input is detected and stored in a content or input table associated with the corresponding language. This has to be done without altering the default mechanisms for accessing user input in modules. I´m not yet sure if this is possible, but I would like to hear ideas about this.
3. Content rendering layer: Before any content is rendered the appropriate content is selected from the content or input table according to the current site´s language.
The language discovery feature of Drupal works just fine, as well as the default most basic language features so those would be reused. We would be avoiding or suppressing the node-level language features.