Hi,
The Core SEF URLs look almost like what you want. Only the product link (via category page) uses the main category name instead of the sub category as you would like. Isn't that good enough ?
If you really want to change that URL to meet your needs, you will have to edit the file components/com_hikashop/router.php but that modification is definitely not simple as it will require that you do mysql queries to get the information you need, but it's doable.
