The IBM mainframe is all about virtualization. Heck, IBM invented it pretty much around the same time that Linus was born. Neat coincidence.
An IT appliance is a system optimized and purposed for a specific set of tasks.
We can build software-only virtual appliances that have the same user experience as the purpose-built hardware version (i.e., IBM WebSphere DataPower CastIron XH35). In both cases, all the "overhead" parts are either ignored, such as network and DNS configuration, or abstracted away from user control, such as disk partition and RAID stuff.
Seems to me like we should be able to take these three threads, and start to build workload-oriented appliances for the mainframe. For example, if you want an MQ-based CICS application behind a load balancer, it should be fairly straightforward to bring up a virtual partition that provides that, and looks and feels like an appliance. If you need more tuning, go to the advanced screen.
So why can't z look like a whole bunch of specialized appliances tuned for various workloads? Why can't the new face of zEnterprise be an appliance one?
Disclaimer: What I know about the mainframe can fit on the head of a pin; heck, I can barely spell