I add OpenVZ repos to the kickstart for the purpose of compiling the .iso. The result being an .iso with a single vzkernel, no stock kernels. When the .iso is used, network isn't needed.
I think whether this is done to create a minimal install .iso or custom live .iso, or whether it's burned on DVD or written to USB, shouldn't really matter..? Or is the minimal install process that different form the live usb/dvd one..? It's late over here, I might be missing something... 
Relevant repo parts from my kickstart:
repo --name=openvz-kernel-rhel6 --baseurl=http://...
repo --name=openvz-utils --baseurl=http://...
and:
repo --name=sl6-base --excludepkgs=kernel,kernel-debug,kernel-debug-devel,kernel-devel,kernel-doc,kernel-firmware,kernel-headers,perf --baseurl=http://...
repo --name=sl6-security --excludepkgs=kernel,kernel-debug,kernel-debug-devel,kernel-devel,kernel-doc,kernel-firmware,kernel-headers,perf --baseurl=http://..