Only volume sys: needs to be mounted at all times, other volumes could be mounted and dismounted by console commands. [And again server class hardware supported physically swapping the dismounted volume]
Last year, to support CableCard / mCard / Tru2Way [the technology has been renamed several times] deployment, we tried to get a Panasonic Tru2Way television for our development lab.
The distributor refused, as the local Cable company [that would be us] did not support Tru2Way
The old CableCard standard was one way only. The newer 'MCard' and the OCAP / Tru2Way boxes are much more capable, and [speaking from the inside of the cable industry] a bit puzzling to deal with.
We are looking at revamping our entire provisioning infrastructure to permit the new generation boxes to function, but that has run into some comical snags. For example, we can't get a Pannasonic Tru2Way set delivered to our lab, because the distributor will only ship to areas served by a Tru2Way compatible cable provider. We're working on it, but we're not fully compatible.
Used to hang out on Will Zachman's Canopus forum, using an off line CI$ agent called 'Golden Compass'
Your good nature will bring you unbounded happiness.