Hi @pcammish, Thanks for getting the UI and documentation looked at.
On the risk of losing data, I can already delete a disk as long as I jump the numerous "Are you really sure?" and "Beware of the leopard" hurdles. So this could be another case for "You asked for it" UI confirmation. What if the disk space to be lost had to be filled with a value, e.g. 0xff if that's good for SSDs, to show I'd already nuked the data and so had nothing to lose?
Interestingly, deleting a VM just asks once if I'm sure then, poof!, it's gone, disks and all.
Alternatively, as the system stands today, can I add a second disk, make it be bootable, e.g. grub in the MBR, etc? If I then make the "root" disk unbootable, will BigV pootle along and use the next disk? If so, I could clone root to a smaller disk and start booting from that instead. This just leaves being able to delete the current root disk, e.g. assign root-ness to another disk and then delete the non-root disk as two UI steps.