Hi,
That's right, there is no feature to assign several product templates to vendors.
It is something in our TODO list but I can't provide any schedule for his implementation.
But even if the feature is not available by default in the component, it could be possible to use a custom plugin to perform the template selection and make an override on the vendor template temporally.
About the problem with the template and the variant generation ; I will mark it as a bug for a future release. I don't think that it would be available for HikaMarket 1.7.0 (roadmap is already full) so it would be more for HikaMarket 1.7.1
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.