While reading qubes os documentations I found:
As a goal to improve Qubes network security, it bring me an idea to try import official images of NGFW from well known vendor(s):
Fortigate as qube template, and it’s alive:
But this template function only as last Qube in chain:
Someone tried to reach fully functional commercial NGFW within Qubes and can share his experience?
I haven’t tried NGFW as firewalls specifically, but for a vm to participate in qubes networking you need to install certain packages (described pretty thoroughly in minimal templates). Currently they’re only shipped for debian, fedora, and whonix officially, and for some other distros in the community.
Maybe you’ll be able to get them working on FortiOS, that would be cool.
You might also be interested in these:
As long as I know there is no option to install linux package in FortiOS, only if company itself integrate qubes-core-agent-networking package into firmware.
Cisco Firepower NGFW and Pan-OS - also
But look like Gaia from checkpoint allow installation of linux packages using expert cli mode 
Gaia appliance OS request only 1 disk pool, so it fail installation process according to exist of root and private disk pools.
Can’t find way to fully remove private pool of template, minimal size is 4M
That is a pretty interesting topic. It is definitely possible to attach an additional volume to a vm, but I’m not sure how the system will react if you delete one of the default volumes instead.
By default qubes storage is lvm over luks. You can manually manage volumes with appropriate lvm commands, like lvs and lvremove. Just be aware that removing volumes that Qubes expects to be there might break stuff, especially in vms that actually use this separation, like AppVMs. Might be better with a standalone…
