Except for the hardware bits, this is a non issue: See Shavlik, Zen (does it still exist?), SCCM, etc.. Hell, my crappy little office (4K users) does patches & updates using a combination of WSUS & SMS. If we really needed to, we could deploy
As far as the hardware goes, In ten years I have very rarely seen shops that actually update hardware. (exceptions to the rule: Computer savy users (eg: (un)helpful admin proxys); admins) Usually the top dogs have their oldish stuff pushed down the line, and stuff gets thrown out when it depriciates: Too much trouble to buy new memory to upgrade. We want everything the same. Like eMnim.
Anyway, that's my $2 The issue that usually kills VDI is licensing. It's an expletive. Out of curiosity, has anyone used any of the application virtualization products? Symantec (slogan: Where good products go to die;) has one where you can roll out apps in a para-virtual manner with delta updates & rollback capabilities. I saw another one recently where a VM with the OS+application stack was pushed to client machines & managed from a central template. (At least that's what the marketing drones said.)