magento - Merchandising categories at store level -

we begin working on addition magento 1.14.2 ee allow merchandise , sort products within categories @ store level. having 3 entirely separate root category trees, our editors finding cumbersome, , our indexing takes 3x time should take reindex single tree.

the plan add store_id column catalog_category_product table stores product_id, category_id , products position within category in question.

so questions general @ point, has attempted , there obvious pitfalls encounter result of attempting this? solution seems obvious yet hasn't been implemented yet magento, surely piece of functionality useful company has presence in multiple countries.