Hi,
HikaShop is already compatible with the Joomla 3 multilanguage system which consists in creating one menu/product/category/article per language. We just don't recommend it as it's a lot of work to create and maintain compared to having simply translations of the content via Falang/JoomFish.
If Falang has errors, I invite you to report them to the developer. He is quite pro active in fixing them and regarding the support of other extensions, it just require the creation of a small xml file (which is actually almost the same as the xml for JoomFish) so it should be easy to add and you can always ask the Falang support for help on this.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.