For the multilanguage aspect. A choice has to be made.
ATM multilanguage an UC is impossible because of the translation nodes drupal creates.

UC can go its own way on translation (field translation?) and circumvent drupal core translation nodes.

Though my opinion is to stick to the drupal core and go with the flow.
In that case im in favour of attaching products to nodes instead of the node being the product.

A lot of work in terms of rewriting sql queries but it seems the most solid solution to me for multilanguage.

Maybe we should create a proof of concept to see if this idea has any future?