In fact your question is different and in your reply, you seem request to have a partial sharing of the VM content.
Today such kind of partial sharing is not possible in VM.
I suspect that you would like to have same websites that share some products depending on the websites or have specific vendor for specific websites.
Such kind of behavior is possible with Hikashop that has the multisites functionality available in their code.
What I can suggest is that you request that to the VM authors.
I can tell you that they know how to modify VM to do that because I teach them at the J "J and Beyond 2013" on how JMS share the info in VM and how to modify their code to acheive such kind of objective.
So if you request that to the VM team, perhaps that they will speed up their development or see the Hikashop solution that can do such kind of thing.
Here it is our hikashop partner ship link
www.hikashop.com/download.html?partner_id=16361
See also our change history that give more info on the Hikashop and hikamarket solution
www.jms2win.com/en/faq/change-history-13...d-hikamarket-sharing