You will need Jms Multisites + the "Article Sharing for JMS'.
It is possible to share the VM and Kunena.
Concerning VM, as you could read at many places in the forum, there are constraints concerning the sharing of some configuration like the Payment Method and the Shipment confgiuration that is common to all the website.
Concerning RoketThemes templates and modules, they have some of them that may not be compatible with JMS. Some other are OK and we have published some patches for some modules.
So check the list of extensions.
www.jms2win.com/component/content/article/135
The advice that I can give you is consider the master website like a repository, a library where you put all the extensions.
In general I recommend to not publish this website.
Use an architecture like the one presented in tutorial video 16
www.jms2win.com/tutorial#jms12x-16
Consider the "Slave 1" like your main website (not the master) - that can be a portal, ...